Application of GIS in Hydrology and Water Management

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					J. Fürst                                                                                                                                     SS 2007

                                                                                    Aim of course

                                                                                      In recent years, Geographical Information Systems
            816.347 Application of GIS in                                             (GIS) have been increasingly used to support
            Hydrology and Water Management                                            hydrological models and water resources
                                                                                      management. The lecture series attempts to
                                                                                      demonstrate how the appropriate use of GIS in
            Josef Fürst                                                               hydrological and water management studies can help
            SS 2007                                                                   to achieve better results more efficiently.

             Subject of course                                                      Organisational issues
                GIS serve multiple purposes in a wide range of spatial problems       Block from April 26 to May 24, 2007
                   specific issues for appropriate application in hydrology and       Thursday, April 26, May 3, 10 and 24: 14:00 – 17:00
                water resources management.
                                                                                      Friday, April 27, May 4, 11 and 18:    10:00 – 13:00
                GIS basics:
                 • Introduction to GIS – Spatial information in hydrology and
                    water management – Data models – Data structures –                Lecture room XXII (on Fridays sometimes SR 02/51)
                    Coordinate systems and map projections - Analysis of spatial
                    data – Overview of GIS software and products                      Course notes:
                GIS in hydrology and water management:
                                                                                      • PPT-Slides
                 • Hydrological models and GIS – Interpolation of hydrological
                    variables – Digital elevation models and their application –      • Book (in German): J. Fürst (2004):
                    GIS support for modelling of surface runoff – GIS support for       GIS in Hydrologie und Wasserwirt-
                    groundwater modelling – GIS in water-related information            schaft. Heidelberg: Herbert Wichmann
                    and decision support systems                                        Verlag. 336 S. € 56.-
                                                                                        (discount – 30%)

816.347 GIS in Hydrology and Water Management                                                                                                     1
J. Fürst                                                                                                          SS 2007

                                                        Learning objectives

                                                          In this section you will learn:
                                                          • Differences between GIS and related computer
            Introduction to GIS                             systems, such as graphics, CAD and DBMS,
                                                          • comprehensive view of GIS consisting of hardware,
                                                            software, data, procedures and expert knowledge,
            Josef Fürst                                   • overview of the range of function and tools in GIS,
                                                            related to tasks in hydrology and water management


                                                    3                                                             4

             Outline                                    Introduction

                Introduction                              growing importance since mid 1980s, in scientific,
                History                                   technical and socio-economic disciplines and public
                Components of GIS                         sector
                  • hardware                              Large number of different products for a large
                  • software                              bandwidth of applications
                Tools (functions) of GIS                  Term „Geographic Information System“ (GIS)
                Summary                                   Related to hydrological and water management

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J. Fürst                                                                    5                                                                   SS 2007

             History                                                            History

                GIS on all categories of computers from super                     Commercially available systems from appr. 1980
                computer to PC and even handhelds                                 (ArcInfo 1981)
                From cartography to integrative tool                              GIS, RIS, LUIS, ...
                Integrated, multi-discipline approach                             GIS for acquisition, storage, analysis, and
                Parallel development in land register (cadastre),                 presentation of spatial data.
                topographic mapping, thematic maps, CAD                           Spatial data are describing elements of reality with
                (Computer Aided Design), geography, mathematical                  respect to
                analysis of spatial variability, soil science, surveying,         • Position within a coordinate system
                remote sensing, imaging, spatial planning                         • Spatial relationship (topology) like neighbourhood,
                                                                                    proximity, ...
                                                                                  • Properties (attributes) like groundwater table, land use,
                                                                                    concentration of pollutants, etc.

                                                                            7                                                                   8

             History                                                            Components of a GIS

                Common elements of GIS and other software systems                 GIS have 5 components
                                                                                  • Computer system (hardware) to store, process and
                                                                                    present digital spatial data,
                                    GRAFIK                                        • Software to perform GIS operations,
                                                                                  • digital geographical data,
                                                                                  • Procedures to complete certain tasks
                         GIS              CAD                                     • Expert knowledge to apply GIS appropriately


                GIS as a model of a part of the world

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J. Fürst                                                                                          9                                                                          SS
                                                                                                                                                                            10 2007
                                                                               GIS components                                                              GIS components
             Hardware                                                                                  Software

               Input devices               Computer                   Output devices
                                             CPU                                                                           Data acquisition               GIS
               Digitizer                Mainframe                      Monitor
               Scanner                  Unix workstation               Inkjet printer
               Digital camera           PC                             Laser printer                     Data query
                                                                                                                            Geographical           Data analysis
               Data on EDP media                                       Offset printing                                       database
               Remote sensing                                          (Plotter)


                                                                                                  11                                                                        12
                                                                               GIS components                                                              GIS components
             Software                                                                                  Software

                data acquisition                                                                        Data management: organisation, structuring and
                  • Digitizer, import of raster data sets (scanner, satellites,                         storage
                    video digitizer), import of external data sets.                                      • Reliable storage,
                  • Error correction, generation of topology, geo-                                       • Efficient access and unified interface for all software
                    referencing (Coordinate system)                                                        components to the data.
                  • Usually more than one source (e.g. groundwater study)                                • Organisation of information about a specific region
                  • Increasing availability of digital data (surveying                                     usually organised by layers
                    services, land register, digital hydrological atlas, remote
                                           Existing maps  Survey data  Remote sensing
                  • Exchange of data

                                                Digitizer   Scanner     EDP media

                                                             Data entry

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J. Fürst                                                                            13                                                                            SS
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                                                                   GIS components                                                               GIS components
             Software                                                                    Software

                Analysis: geographical database turns into an                              • What is the value of function z at location x? E.g., the
                information system                                                           groundwater tables at some wells are given. For
                  • Where is object A? The GIS reports the coordinates,                      location x, the value of function z, here groundwater
                    e.g., of a monitoring site, or displays a map whith the                  table, is to be interpolated.
                    object highlighted                                                     • How large is B? Area, perimeter and length are often
                  • Where is A in relation to B? The potential polluter (A) is               automatically managed by GIS. Used, e.g. to evaluate
                    within (outside of) the wellhead protection area (B)                     areal statistics for time-area diagrams.
                  • How many objects of type A are within a distance D of                  • Which objects are adjacent to objects with a given
                    B? How many monitoring wells (A) are available within                    combination of properties? Which land parcels are
                    the estimated extent (D) of a well‘s cone of depression?                 crossed by a planned irrigation canal?
                       buffer zones around object                                          • Combination of objects with a given combination of
                                                                                             properties. Suitability of land for a desired use.

                                                                                    15                                                                           16
                                                                   GIS components                                                               GIS components
             Software                                                                    Software
                  • What is the result of the overlay of 2 maps? Logical                  Presentation component
                    combination (overlay) of information layers („thematic
                    maps“), to derive new spatial information.                                      Data output and presentation

                    Karte 1
                                                C                                                                               EDP media
                                                                                              Screen         Printer                           Plotter

                    Karte 2
                                                                                             Thematic maps             Tables               Graphics


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J. Fürst                                                                          17                                                          SS
                                                                                                                                             18 2007

             Tools (functions) in GIS                                                  Summary
                Differences in the focus depending on specific software product         GIS are computer based systems to acquire, manage,
                  • E.g. ArcInfo Workstation:                                           analyse and present spatial information.
                      •   Data capture and automation
                                                                                        Development started in the 1960‘s, breakthrough in
                      •   Error refinement and verification
                      •   Coordinate transformation                                     widely spread application in environmental
                      •   Topology generation and update                                information systems occured in the 1980‘s.
                      •   Generalization tools                                          A GIS should be seen not only as a software
                      •   Attribute automation and update
                      •   Database construction                                         package, but rather as a comprehensive system,
                      •   Analysis and manipulation                                     consisting of hardware, software, data and users.
                      •   Display and query
                      •   Using menus
                      •   Dynamic segmentation
                      •   GRID analysis
                      •   IMAGE analysis
                      •   Database integration
                      •   TIN

816.347 GIS in Hydrology and Water Management                                                                                                      6
J. Fürst                                                                                                             SS 2007
                                                        Learning objectives

                                                          In this section you will learn:
            Spatial Information in Hydrology and          • Overview of commonalities in GIS technology and
            Water Management                                hydrology to motivate for GIS use in hydrology and
                                                            water management.
                                                          • Basic understanding of modelling with spatial
            Josef Fürst                                     information
                                                          • Overview of properties of spatial information in
                                                            hydrology and water management


                                                    3                                                            4
             Outline                                    Introduction

                Introduction                              Establish a relationship between problems in water
                Motivation                                resources and the capabilities of GIS by comparison
                Data and information                      of terms and schematic figures
                Problems                                  Discrimination between „Data“ and „Information“
                Summary                                   Characterisation of hydrological information

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J. Fürst                                                                                                                                                                                             SS 2007
                                                                                                              5                                                                                  6
             Motivation                                                                                           Motivation

                Concordance between tasks in hydrology and water                                                    Concordance between tasks in hydrology and water
                management and functionality of GIS technology                                                      management and functionality of GIS technology

                  Hydrologie und Wasserwirtschaft            GIS                                                    Schematic illustration of the hydrologic cycle   The „world“ in GIS (ESRI,
                                                                                                                    In a text book of hydrology                      1998):
                  „Die Hydrologie ist die Wissenschaft vom   „Ein raumbezogenes Informationssystem
                  Wasser, seinen Erscheinungsformen          dient der Erfassung, Speicherung,                      (Bras, 1990):
                  über, auf und unter der                    Verarbeitung und Darstellung aller Daten, die
                  Landoberfläche und seinen                  einen Teil der Erdoberfläche und die
                  Eigenschaften sowie seinen natürlichen     darauf befindlichen technischen und
                  Zusammenhängen.“ (Maniak, 1992)            administrativen Einrichtungen sowie
                                                             ökonomische und ökologische
                                                             Gegebenheiten beschreiben.“ (Bartelme,
                  „Wasserwirtschaft ist die zielbewußte      „An organized collection of computer
                  Ordnung aller menschlichen                 hardware, software, geographic data, and
                  Einwirkungen auf das ober- und             personnel designed to efficiently capture,
                  unterirdische Wasser. Sie gleicht die      store, update, manipulate, analyze, and
                  Spannungen zwischen dem natürlichen        display all forms of geographically referenced
                  Wasserhaushalt und den ständig             information.“ (ESRI, 1990)
                  wachsenden Ansprüchen des Menschen
                  an das Wasser aus.“ (Maniak, 1992)

                                                                                                              7                                                                                  8
             Motivation                                                                                           Data and information

                Concordance between tasks in hydrology and water                                                    Data
                management and functionality of GIS technology

                  Hydrologisches Modell SHE (Bathurst &       GIS-Überlagerung (Vieux, 1992):
                  O’Connell, 1992):

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J. Fürst                                                                                                                     SS 2007
                                                                                9                                       10
             Data and information                                                    Data and information

                Data + Knowledge                                                       Data + Knowledge = Information


                                                                                11                                      12
             Data and information                                                    Data and information

                Data + Knowledge = Information
                  • E.g.: a sequence of coordinates describes a polyline (=
                    data). Knowing that this polyline represents a reach of a
                    river, creates knowledge of it.
                  • The model concept determines data requirements
                  • e.g: the unit hydrograph contains information about the
                    catchment‘s reaction to rainfall, which depends on
                    shape, size, height, vegetation, geology, slopes, etc.,
                    without having to know these factor zu develop the UH
                       it is a„model of the catchment“ and has a spatial
                  • Models with distributed parameters use a spatially
                    distributed characterisation of catchment properties

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J. Fürst                                                                                                                                                 SS 2007
                                                                         13                                                                         14
             Data and Information                                             Problems

                                                                               Water resources management
                                                                                • Goal-oriented order of human impacts on surface and
                                                                                  subsurface water. Compensation of conflicts between
                                                                                  natural water supply and anthropogenic demands
                                                                                • Uses and functions
                                                                                   • Domestic and industrial water supply, cooling water,
                                                                                     irrigation, flood protection, hydro power, navigation, water
                                                                                     quality, including sewage treatment and low flow
                                                                                     regulation, recreation, fishing, drainage, erosion,
                                                                                • Protection and enhancement
                                                                                   • Natural water bodies, archeological, historical, biological
                                                                                     and geological resources, eco-systems, quality of water,
                                                                                     land and air.
                                                                               GIS supports inter-disciplinarity


                Many developments in GIS technology originate from
                environmental and natural sciences       use of GIS in
                hydrology and water management natural
                Hydrologic models are based on information about
                the area, for which hydrologic processes are to be
                described. The model concept determines, in which
                form the area characteristics are to be made available
                important hydrologic information: Time series,
                drainage network, land use, elevation model,
                Spatial hydrologic information is basis for water
                management planning, both for use and protection of
                water resources and the environment

816.347 GIS in Hydrology and Water Management                                                                                                                10
J. Fürst                                                                                                                              SS 2007

                                                                        Learning objectives

                                                                          In this section you will learn:
            Data models: Formal Abstractions of                           • how the conceptual perception is already based on a
            Reality                                                         model of space,
                                                                          • how this conceptual perception determines the
                                                                            selection of an appropriate data model, and
            Josef Fürst                                                   • how the selection of a particular data model influences
                                                                            the appropriate data types to represent the phenomena
                                                                            of interest and the possible spatial analyses.


                                                                    3                                                                 4

             Outline                                                    Introduction

                Introduction                                              ‘Models‘ are created from key features
                Conceptual models of real world geographical              • What we regard as the respective key characteristics
                phenomena                                                   and how we build the model, depends on our cultural
                Data types                                                  background and the purpose of the view.
                                                                          • ‘A fisherman’s view of a river is different from an
                Axioms and procedures for processing spatial data
                                                                            engineer’s view’
                Data models and spatial analysis                          • Should the Danube be seen as a polyline, a waterbody,
                Applications of data models                                 a trench in the earths’s surface or a place to live for
                Summary: Entities or continuous fields?                     animals and plants? Is it an exactly defined and
                                                                            bounded object or rather given by the continuously
                                                                            varying field of the river bed’s elevation?
                                                                          Conceptual models of space:
                                                                          • entities
                                                                          • continuous fields

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J. Fürst                                                                                         5                                                                                                       SS 2007
                                                                                                                                                                                 Conceptual models ...
             Conceptual models of space                                                              Entities or continuous field?

                2 questions                                                                            Pragmatic decision, determined by the application,
                   • What is present?    house, river, ...                                             In administration rather entities, in science more often
                   • Where is it?   coordinates                                                        continuous fields
                Entities:                                                                              Examples:
                   • Collection of objects (entities): Definition and                                   Administrative information                 Geo-hydrological information
                     recognition (house, utility line, forest, river, etc.);                                              Planning zones                             Terrain elevation
                     Properties to describe boundaries and position
                continuous fields                                                                                         Land register                              Soils

                   • Continuous function of cartesian coordinates in 2, 3 or 4
                     (if time is included) dimensions                                                                     Utility lines                              Rivers

                   • The variable is a „smooth“ function, continuously
                     varying in space                                                                                     Geodetic survey points                     Groundwater levels

                                                                                                                          Subsoil surveys                            Boreholes

                                                                                                 7                                                                                                       8
             Geographical data models and                                Conceptual models ...                                                                                   Conceptual models ...
                                                                                                     Vector data models of entities
             geographical data primitives
                geographical data primitives : points, lines, polygons                                 simple points, lines and polygons
                                                                                                       complex points, lines, polygons and objects
                           a a1 a2 …            a a1 a2 …                a a1 a2 …
                                                                                                        • More complex definitions of points, lines and polygons
              y7                        y7 1                    y7                                        can be used to capture the internal structure of an
                                    d              2
               6            c            6 a           5         6                                        entity; functional or descriptive.
               5       a                 5                       5                                      • E.g.: ‘city’ contains streets, houses and parks, each
                                              3c     d
               4                         4                       4                                        having different functionality and may respond differntly
               3                         3     e                 3                                        to queries or operations.
                                b             6
               2                         2                       2
                   1 2 3 4 5 6             1 2 3 4 5 6               1 2 3 4 5 6                        • Object-oriented systems support a hierarchical
                             x                          x                      x
                                                                                                          construction of objects from simple building blocks and
                                                                                                          a framework for description of properties as well as

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J. Fürst                                                                     9                                                                                    SS
                                                                                                                                                                 10 2007
                                                     Conceptual models ...                                                               Conceptual models ...
             Models of continuous fields                                          Raster or vector model?

                Triangulation                                                        Raster model can also represent points, lines and
                Raster (grid)                                                        polygons
                                                                                     Loss of spatial resolution, because location is only
                                                                                     expressed by multiples of pixel size
                                                                                     Contour maps: Entities or fields?
                                                                                     e.g: soil map

                                                                             11                                                                                  12
             From observation to standardized data   Conceptual models ...

             models                                                               Data types
                                                                                  Data type   Allowed values       Allowed operations

                                                                                  Boolean     0 or 1               Logical and indicator
                                                                                                                   operations: true or false
                                                                                  Nominal     Any names            Logical operations,
                                                                                                                   classification and identification
                                                                                  Ordinal     Numbers from 0 to    Logical and ranking operations,
                                                                                                                   comparison of magnitude
                                                                                  Integer     Whole numbers from Logical operations, integer
                                                                                              - to               arithmetic
                                                                                  Real        Real numbers from    All logical and numerical
                                                                                              - to                 operations

816.347 GIS in Hydrology and Water Management                                                                                                                         13
J. Fürst                                                                         13                                                                     SS
                                                                                                                                                       14 2007
             Axioms and procedures for handling                                       Axioms and procedures for handling
             data in information systems                                              data in information systems
             1. We need discrete primitives to carry information                      7. New entities can be created by geometrical union or
                (entities): points, lines, polygons.                                      intersection
             2. Primitives are defined in terms of location, attributes               8. New complex objects can be created from basic
                and relationships (topology).                                             entities points, lines, polygons, pixels.
                                                                                      9. New attributes can be derived from existing attributes
             3. Entities are distinguishable by their location, their
                                                                                          by logical and/or mathematical procedures.
                attributes or by their internal or external relationships.
                                                                                      10. Entities having certain defined sets of attributes may
                Primitives are internally homogeneous.                                    be kept in separate sub-data sets called data planes
             4. Entities and attributes can be classified into useful                     or overlays (layers).
                categories.                                                           11. Data at the same XYZ-coordinate can be linked to
             5. Boolean algebra can be applied on entities, attributes                    all data planes (the principle of the common basis of
                and relationships                                                         location).
             6. GIS can perform extended operations:                                  12. New attributes at any XYZ location can be derived
                  •   distance, direction, connectivity, adjacency, proximity,
                                                                                          from a function of the surroundings (e.g. computation
                                                                                          of slope, aspect, connectivity).

                                                                                 15                                                                    16

             Data modelling and spatial analysis                                      Examples for the use of data models

                There are links between the selected data model, the                    Water bodies
                data types and the possible analyses                                     • Changing water levels in lakes, reservoirs or rivers can
                  • If location and shape of an entity are time-invariant and              change their size, shape and position
                    exactly known        Vector model.                                   • During flood events, rivers can change their path
                  • If attributes are fixed, but the entity may change shape               (breakthrough of meanders, new reaches)        change of
                    but not position (e.g. drying up of a lake)    Raster                  geometry and topology!
                    model                                                               Continuous fields in hydrological models
                  • If attributes can vary, object changes position, but not             • Continuous fields in GIS only spatially discretized (TIN,
                    shape       behaviour can be represented by object-                    raster)
                    oriented models                                                      • Dimension of time not represented
                  • If no clear entities can be discerned, then often a
                    discretized, continuous field is preferable

816.347 GIS in Hydrology and Water Management                                                                                                               14
J. Fürst                                                                         17   SS 2007

             Summary: Entities or continuous fields?

                  Representation of reality in a data model requires 3
                  1. Conceptual model of the „world“ (Entities
                     continuous variation)
                  2. Data model: collection of discrete objects
                     smooth continuous field
                  3. Representation
                      •   Entities: primitives, combinations of them or
                      •   Fields: a) discrete; b) differentiable, mathematical
                          functions; c) non differentiable functions
                  conversion vector – raster is irreversible
                  administration: entity model preferred
                  sciences, dynamic processes: continuous fields
                  (mostly raster)

816.347 GIS in Hydrology and Water Management                                             15
J. Fürst                                                                                                                                        SS 2007

                                                                             Learning objectives

                                                                               In this section you will learn:
                                                                               • Understanding of important geographical data
            Data Structures                                                      structures and their relevance,
                                                                               • Importance of topology and its utility for spatial analysis,
                                                                               • Relevance and implementation of thematic information
            Josef Fürst                                                          (attributes)
                                                                               • Recognition of thematic hierarchies and their robust
                                                                                 and efficient representation
                                                                               • Basic concepts of relational databases,
                                                                               • Advantages and disadvantages of vector and raster
                                                                                 data structures.

                                                                         3                                                                      4

             Outline                                                         Introduction
                Introduction                                                   Data models are independent of a specific
                Levels of creating a model                                     implementation in a GIS. Also analogue maps are
                Coding the basic data models for input to the computer         based on models of the area.
                Data organisation in vector data structures
                                                                               digital coding of the information, in several stages
                Object oriented data structures
                Data organisation in raster data structures
                                                                               from the data model, data structures, data types up to
                Images                                                         their binary representation
                Compact storage of raster data                                 We need efficient data structures, that
                Storage of vector and raster data in DBMS                      • represent the selected data models completely and
                Attributes                                                       unambiguously,
                Attributes and topological consistency                         • are robust,
                Database management systems (DBMS)                             • efficiently support the desired analyses and
                Vector versus raster data structures                           • use storage space economically.
                Data exchange, standardization

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J. Fürst                                                                       5                                                                                SS 2007
                                                                                   Coding the basic data models for input
             Levels of creating a model
                                                                                   to the computer
             1. A view of reality; the conceptual model.                             discrete primitives of geographical data to create
             2. Human conceptualization leading to an analogue                       entities as well as continuous fields
                abstraction (analogue model).                                        Representation of position, relationships and
             3. A formalization of the analogue abstraction without                  attributes of different types
                any conventions or restrictions of implementation                    Points, lines and polygons are the spatial primitives in
                (spatial data model)                                                 a vector model, pixels in raster models.
             4. A representation of the data model that reflects how                 Spatial relationships between entities are defined by
                the data are recorded in the computer (database                      topology
             5. A file structure (physical computational model)
             6. Accepted axioms and rules for handling the data
             7. Accepted rules and procedures for displaying and
                presenting spatial data (graphical model)

                                                                               7                                                                                8
             Data organisation in vector data                                                                                            Data organisation in
                                                                                   Points                                                vector data
             structures                                                                                                                  structures...

                Vector-based geographical databases are composing                    Position of points is defined by a single pair of
                a complex theme of several layers, each of which                     coordinates (X, Y)
                combines a certain class of phenomena.                               Additional info: type of point, attributes
                  • E.g. hydrological map: rivers, lakes, observation sites,         Layer of point entities created from simple table
                    land use, etc., each in a separate layer                         • E.g. event theme in ArcView
                Layer (Coverage) consists of entities of one type, with
                relationships, different attributes
                Layers are handled independently from each other                        y7
                                                                                                            d        #    X Y      A B
                  • E.g. data structure does not force a gauge to be on the              6          c                1   2.2 4.1   a r
                    river bank                                                           5      a                    2   4.2 2.6   b s
                Vector-GIS use implicit relations (tables) for storage                   4
                                                                                                                     3   3.4 5.4   c t
                Software packages use different structures.                              3
                                                                                                        b            4   5.2 6.1   d u
                                                                                             1 2 3 4 5 6
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J. Fürst                                                                                 9                                                                                               SS
                                                                                                                                                                                        10 2007
                                                                  Data organisation in                                                                           Data organisation in
             Lines                                                vector data                 Networks                                                           vector data
                                                                  structures...                                                                                  structures...

                Sequence of (X, Y) coordinate pairs and connecting                             Information about connectivity with other line entities
                straight lines or curves                                                       to represent street networks, utilities, rivers
                                                                                               topological information in the data structures
                                      #1:       #2:
                 y7                                                                            connectivity tables
                                       X Y       X Y      # A B
                  6                                                                            Topological terms: „node“ and „arc“
                         1            2.2 4.1   4.2 2.6   1 a r
                               2          5.4       4.3   2 b s                                arc-node topology
                                                5.2 6.1
                  3                                                                             y7 1
                  2                                                                                    2                    Arc# From#         To#
                      1 2 3 4 5 6
                                                                                                  6 a              5
                                                                                                          b                   a           1     3
                                                                                                       3c       d             b           2     3
                                                                                                        4                     c           3     4
                                                                                                  3     e
                                                                                                       6                      d           5     4
                                                                                                    1 2 3 4 5 6               e           4     6

                                                                                         11                                                                                             12
                                                                  Data organisation in                                                                           Data organisation in
             Polygons                                             vector data                 Polygons                                                           vector data
                                                                  structures...                                                                                  structures...

                Shape, neighbours, hierarchy                                                   Polygons with point dictionaries
                simple polygons: sequence of x,y coordinate pairs                               •    Points with ID in a list (table)
                  • Border lines between polygons are digitized and stored                      •    Polygons as ordered list of pointers into list
                    twice. Error: gaps, overlaps                                                •    Borders between neighbouring polygons are unique.
                  • No information on neighbourhood.                                            •    no information on neighbourhood
                  • islands only graphically represented.                                       •    No islands
                  • Difficult to validate                                                                           4                        Line dictionaries
                                                                                                           3                                           L1

                                                                                                13              9                        6

                                                                                                                                                            L4                  L2
                                                                                                                                     7                                L6
                                                                                                                            10                 L3
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J. Fürst                                                                                                                            13                                                                                         SS
                                                                                                                                                                                                                              14 2007
                                                                                                             Data organisation in                                                                      Data organisation in
             Polygons                                                                                        vector data                 Storage without redundancy                                    vector data
                                                                                                             structures...                                                                             structures...

                Polygons by arc-node-topology                                                                                              Sequential transformation of coordinates
                  • Underlying principle: free of redundancy                                                                               No change of topology
                                                                                                                                           • E.g. plans of Vienna metro:

                                                                                                                                    15                                                                                        16
                                                                                                             Data organisation in                                                                      Data organisation in
             Triangulation of continuous fields                                                              vector data                 Triangulation of continuous fields                            vector data
                                                                                                             structures...                                                                             structures...

                Node list and triangle list
                                                                                                                                           efficient TIN models: select nodes in order to
                             1                                                                                                             represent surface with a minimum number of points
                                                                              TIN list of triangles
                                         A                                    Triangle Node list       Neighbours                          dense points where relief of surface is rapidly varying,
                                                                                  A     1,2,3             -,B,F                            scarce points in flat areas
                                 F                           C                    B     2,4,3             -,C,A
                                                                                  C     4,5,3             -,D,B                            Consideration of breaklines
                 8                               3                                D     5,6,3             -,E,C
                                                     D               5                                                                                        2                                        2
                                         E                                        E     3,6,8            D,G   ,F                                                                      breakline
                             G                                                    F     1,3,8             A,E,-                                    1                               1
                                             6                                   G      6,7,8              -,-,E                                                   4                                                4
                         7                                                                            - no neighbour
                Optimal TIN by Delaunay criteria
                     2 possible triangulations           This triangulation fails the         This triangulation satisfies the
                     for 4 given points                  Delaunay criteria, because the       Delaunay criiteria because a                 8              3                8                       3
                                                                                                                                                                       5                                                 5
                                                         circle around triangle 1, 4, 3       circle around each triangle
                                                         contains node 2.                     contains no other node
                                         2                                    2                                   2                                       6                                        6
                     1                                                                        1                                                                                                            inserted
                                                         1                                                                                     7                               7                           edge of triangle
                                                     4                                                                      4

                                     3                                    3                                   3

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                                                                                                                                              18 2007

             Object oriented data structures                                  Object oriented data structures

                Object oriented systems encapsulate data objects                UML (unified modeling language) diagram of a part of
                together with methods applicable to them. Access to             a geodatabase
                objects is only done by the methods defined for them
                Data structures get a defined behaviour
                  • „Hydrant“ should delete itself, when the last pipe
                    connecting it to the network is removed.
                Structural object orientation: capability, to create
                composed objects (Arc Hydro)
                Behavioural object orientation: behaviour of data
                types with specifically defined functions and
                CASE-Tools (Computer Aided Software Engineering)
                for design and implementation

                                                                         19                                                                   20
                                                                              Data organisation in raster data
             Object oriented data structures
                Arc Hydro                                                       Raster resembles photo

                                                                                3 ways to interprete a pixel
                                                                                • classification: a range of values is allocated to certain
                                                                                  objects (gray pixels are roads, blue pixels are water
                                                                                • measure the value: intensity of a colour, concentration,
                                                                                • relative height over reference height.

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                                                                                                                                                                                                       22 2007
                                                                                              Data organisation in                                                            Data organisation in
             Raster data structure                                                            raster data structures        Raster data structure                             raster data structures

                Position is represented by discrete cells                                                                     Entities also in raster model
                  Origin (upper left cell)                                Value Land cover
                                                                            1      forest
                                                                            2    grassland
                                                                            3    farmland


                                                Cell size
                           Columns                                                                                            Cell size determines resolution: cell size max. 50% of
                Types of raster maps                                                                                          smallest recognized object
                  • Nominal data like land use (forest, grassland, farmland,
                  • Continuous values, concentration, light intensity
                  • relative measures like elevation.

                                                                                                                       23                                                                              24
                                                                                              Data organisation in
             Raster data structure                                                            raster data structures        Images

                Topology described implicitly by raster                                                                       Pictures can be used as map displays (e.g. satellite
                                                       column j                                                               image, orthophoto) or also as attribute information
                                          j-1 j       j+1
                                                                                                                              (e.g. pictures of the measuring instruments linked to
                                                                                                                              the measuring points on a measuring point map,
                      i+1                                                                                                     photo of the houses in the information system of a
                                                                                                                              real estate agent).

                 row i
                Cell raster – point raster
                                     25    40    55   50                  45   55   35   25

                                     15    33    40   35                  35   45   23   15

                                     10    20    25   20                  20   25   20   15

                                     Zellraster                          Punktraster
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                                                                                                                                                              26 2007
                                                                         Images                                                                      Images
             Storage of images                                                         Georeferencing of images

                Similar to raster maps, with some specific properties                    Most image formats, even purely graphic formats
                Pixel (from picture element)                                             usable (e.g. TIFF, JPEG, PCX, GIF, BMP, etc. )
                Economical storage                                                       If image is oriented along coordinate axes:world-file,
                  •   1, 8, 24 or 32 bit for coding of a colour value                    header
                  •   Number of bits per pixel: colour depth                             Georeferencing can be complex
                  •   monochrome, grayscale, RGB, CMY, CMYK                              distortions, e.g. in images from airborne sensors
                  •   Use of a lookup table
                                                                                          a) Abdriftfehler   Flugrichtungs-   Längsneigungs- Querneigungs-
                      Image                     Display lookup table                                         fehler           fehler         fehler
                                                                                                (x)            (x)              (x)             (x)
                       2   7 14 12 8            pixel value   red green blue
                                                     1          0   0     0
                       5 10 9      8   1             2         10 35      5
                                                     3         15 20     21               b)
                       4   5   6   3   9
                                                     4        123 210 33
                       15 13 16 5      5              .         .   .     .
                                                      .         .   .     .               c)
                       2   1 11 9      1
                                                    16        255 255 255

                                                                                  27                                                                          28
             Georeferencing of images                                                  Compact storage of raster data
                Depending on the orientation of the coordinate                           Storing full matrices is not
                system, objects equal in nature are represented                          economical
                differently in the raster model                                          Position, resolution and dimension of
                                                                                         a raster are defined in a header

                If distortions of image are small (flat terrain)
                   georeferencing by affine projection with >= 4
                ground control points (polynomial transformation).
                Pixel are re-computed by interpolation or areal
                averaging, according to the type of variable     loss of

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J. Fürst                                                                                                                29                                                                                  SS
                                                                                                                                                                                                           30 2007
                                                                                                     Compact storage                                                                     Compact storage
             Storage without loss of information                                                                              Storage without loss of information

                Chain codes                                                                                                     Run-length encoding
                  • Cityblock, chequer-board
                                                                                                                                 0     0      0      0   1   1            4*0,2*1,
                 y           j
                             1 2 3 4 5 6 7                                                                                       2     2      1      1   1   2            2*2,3*1,2,
                     i   1                                    Wiese          Wald: (2,4)                                                                                  3*0,2*1,2,
                         2                                                   1,1,2,2,2,3,0,3,0,3.                                0     0      0      1   1   2
                                                              Wald                                                                                                        2,3*0,2*1,
                                                                  00=0                                                           2     0      0      0   1   1            2*2,0,3*1
                         5                                                                                                       2     2      0      1   1   1
                                                          11=3               01=1
                         7                                        10=2
                                                      x                                                                         Block codes are an extension of run-length encoding
                                                                                                                                in 2 dimensions

                                                                                                                        31                                                                                 32
                                                                                                     Compact storage                                                                     Compact storage
             Storage without loss of information                                                                              Storage without loss of information

                Quadtrees                                                                                                       Two-dimensional orderings
                  • Hierarchical data structure                                                                                 • Schemes for order of pixels, to avoid reading excessive
                  • Parts can be addressed and read directly                                                                      data if an arbitrary part of the image is needed
                  • Read only for required resolution
                             1             2
                                                              1          2

                 3 4 7            8
                 5 6 9           10
                                      16 17                                                                                          Zeilenweise             Zeilenweise bidirektional
                                                                      11                    16      17     18
                     12          13        19 20
                 11 14           15
                                      18   21 22   3 4 5 6 7 8 910            12 13 14 15                       19 20 21 22

                                                                                                                                     Peano-Hilbert           Morton

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                                                                                                                                                                         34 2007
             Compression of raster data with loss                Compact storage        Storing vector and raster data in
             of information                                                             DBMS
                Wavelet approximation: JPEG not appropriate for                           Efficient access to large volumes of data with
                GIS:                                                                      complex relationships
                                                                                           • B-Trees
                                                                                           • R-Trees
                                                                                           • Use of DBMS
                                                                                          Geo-relational model
                                                                                           • Hybrid concept: geometry data in vendor-specific binary
                                                                                             format, attributes in RDBMS (INFO, ORACLE,
                ECW (Enhanced Compressed Wavelet)                                            INGRES, INFORMIX, MS ACCESS)
                MrSID (Multi-resolution Seamless Image Database)                                • Storage of attribute data independently from spatial data
                                                                                                • extension, updating, deletion of attribute data do not
                                                                                                  influence spatial data
                                                                                                • Commercial RDBMS ensure use of latest developments
                                                                                                  and standardisation
                                                                                                • Use of standard query language like SQL

                                                                                   35                                                                                    36
                                                                                                                                                 Attribute information
             Attribute information                                                      Attribute information in a raster model

                Geoinformation is based on two main elements                              Geometry and topology determined by definition of
                  • Geometry and topology (Question: Where?) and                          the raster (origin, resolution)
                  • Thematic information (attributes) (Question: What?).                  Attribute information is additional dimension
                Approach via thematic maps
                  • Analogy of transparencies

                                  Thema 1

                                                                                          Spatial query, thematic query, and combined query




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                                                                                                    Attribute information                                                                                  Attribute information
             Thematic information in vector models                                                                               Thematic hierarchy

                A theme is assigned to each topological object (node,                                                              Hierarchy: A catchment of order 1 (counted from
                edge, polygon) by one or more attributes (often tied to                                                            confluence), consists completely and uniquely of
                a label point)                                                                                                     catchments of order 2, etc.
                                                                  1                                                                Similarly administrative units: Province(Land) –
                                            2     1
                           A1, A2, …                                         A1, A2, …                                             County (Bezirk) – Community (Gemeinde)
                    PI D
                                       3          A1, A2, …       P ID
                                           LI D               2          3                                                                 Land                                       OÖ

                M:N relationship between different
                thematic layers     resolve into                                                                                        Bezirk                 Urfahr               Freistadt            Perg
                n units with 1:M relationship

                                                                                                                                      Gemeinde                Grünbach              Lasberg            St. Oswald

                                                                                                                            39                                                                                                     40
                                                                                                    Attribute information                                                                                  Attribute information
             Thematic hierarchy                                                                                                  Thematic hierarchy

                Appropriate data model:                                                                                            Layer structure: each layer is a self-contained dataset
                  • Simple query of information on each level                                                                      (e.g. shapefile), technically independent from other
                  • consistent information                                                                                         levels    quick, direct query, possibly inconsistent
                Layer structure: separate, technically independent                                                                 Tree structure: Information on objects in higher level
                layers for each level                                                                                              must be aggregated on demand          more compute-
                Tree structure: Hierarchy is modelled by building                                                                  intensive, but always consistent
                objects from smallest units (communities     counties                                                                 Ebene 1                                              Ebene 1

                   provinces)                                                                                                                                                              1:M
                  • Decision, which approach is implemented, depends on
                                                                                                                                                  Ebene 2                                  Ebene 2
                    problem and application                   Ebene 1                                        Ebene 1

                                                                                                             1:M                     1:M                                                   1:M

                                                                                   Ebene 2                   Ebene 2
                                                                                                                                                  1:M                    Ebene 3           Ebene 3
                                                              1:M                                            1:M

                                                                                   1:M        Ebene 3        Ebene 3                                                     1:M               1:M

                                                                                              1:M            1:M
                                                                                                                                     Topologie    Topologie             Topologie          Topologie
                                                              Topologie           Topologie   Topologie      Topologie

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                                                                                                                                                         42 2007
                                                                Attribute information        Thematic information and topological
             Thematic attributes
                thematic attributes quantitatively classify objects, e.g.,                     Consistency of data is one of the most important
                a land parcel is attributed by ID, area, prize, owner,                         criteria of an information system. It must be warranted
                address, etc.                                                                  when new data are added as well as after updates
                Logically organized in tables
                A key-field uniquely relates attributes and topological
                obligatory and optional attributes
                computed attributes (area, length)
                Hierarchical inheritance of attributes in object-oriented

                                                                                        43                                                               44
             Thematic information and topological                                            Thematic information and topological
             consistency                                                                     consistency
                Topology-                                                                      Topology-
                rules in                                                                       rules in
                ArcGIS 8.3                                                                     ArcGIS 8.3

                Polygons:                                                                      Lines:

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                                                                                                                                                                                         46 2007
             Thematic information and topological                                                                     Database management systems
             consistency                                                                                              (DBMS)
                Topology-                                                                                              GIS (esp. vector-GIS) use DBMS for long term
                rules in                                                                                               storage
                ArcGIS 8.3                                                                                              • Strict separation of data and application programs,
                                                                                                                        • individual view of data for different users,
                Points:                                                                                                 • Queries, updates, changes only by well-defined
                                                                                                                          interfaces, together with validation of user‘s access
                                                                                                                          rights as well as consistency of data
                                                                                                                       relational database model: all data in table format,
                                                                                                                       relationships only implicitly by values

                                                                                                                 47                                                                      48
                                                                                                          DBMS                                                                    DBMS
             Normal forms                                                                                             Normal forms

                stable data structures should follow some principles,                                                  2. Normal form, if:
                esp. Non-redundancy                                                                                     • 1. Normal form and,
                1. normal form, if:                                                                                     • Each column functionally fully depends on a key field
                  • links between data are made by logical pointers, not by
                    physical address,                                                                                      Gemeinde       Grundstücksnr.    Verkehrswert Bezirk
                                                                                                                           Lasberg        1                 1000         Freistadt
                  • each table has a primary key,                                                                          Lasberg        2                 1500         Urfahr
                  • each column (field) has a unique name.
                                                                                                                           •Delete column „Bezirk“ (county) and create second
                     Bundesland              Hauptstadt      Gemeinde 1                Gemeinde 2   usw.                   table :
                     Oberösterreich Linz                      Lasberg                  Grünbach     ...
                     Niederösterreich St. Pölten              Klosterneuburg           Gugging      ...                     Gemeinde      Bezirk
                                                                                                                            Lasberg       Freistadt
                     Must be resolved to:                                                                                   Reichenthal   Urfahr
                     Bundesland         Hauptstadt        Gemeinde         Bundesland
                     Oberösterreich     Linz              Lasberg          Oberösterreich
                     Niederösterreich   St. Pölten        Grünbach         Oberösterreich
                                                          Klosterneuburg   Niederösterreich
                                                          Gugging          Niederösterreich

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                                                                                                                                                                          50 2007
                                                                                    DBMS                                                                   DBMS
             Normal forms                                                                        Relational algebra

                3. Normal form, if:                                                                 Elementary operations of relational algebra
                  • 1. and 2. normal form and,                                                       • Union is equivalent to union in set theory (all records
                  • No column is transitively depending on a key field                                 from 2 equivalent tables)
                                                                                                     • Difference of 2 relations A and B is composed of those
                       Gemeinde             Bundesland    Hauptstadt                                   records in A which are not in B
                       Lasberg              Oberösterreich Linz
                       Grünbach             Oberösterreich Graz                                      • Projection is a selection of columns of a table
                                                                                                     • Selection is a subset of records which meet given
                     Must be resolved in 2 tables:                                                     logical conditions
                     Gemeinde         Bundesland            Bundesland         Hauptstadt            • Cartesian product of 2 relations results in a table where
                     Lasberg          Oberösterreich        Oberösterreich     Linz
                     Grünbach         Oberösterreich        Niederösterreich   St. Pölten
                                                                                                       record of A is related to each record in B. Important
                     Klosterneuburg   Niederösterreich                                                 special case: JOIN; links tables by common values
                     Gugging          Niederösterreich
                                                                                                     • standardised query language SQL („Structured Query

                                                                                            51                                                                            52

             Vector versus raster data structures                                                Vector versus raster data structures

                Decision depends on classes of represented objects                               Vector data structures              Raster data structures
                  • Linear phenomena are better handled in vector nodels                         Advantages                          Advantages
                  • Raster model has advantages with areal data                                  Good representation of the entity   Good representation of
                                                                                                 data model.                         continuous fields.
                  • If high positional accuracy is important, rasters need too
                                                                                                 Compact data structure.             Simple data structure.
                    much storage
                                                                                                 Explicit description of the         Situation-specific manipulation of
                Applications define the criteria                                                 topology, therefore good support    attribute data is very simple.
                  • Coordinate transformation is easy in vector models                           of network analyses.                Many kinds of spatial analysis
                  • Coordinate transformation is more difficult for raster                       Simple coordinate transformation    and filtering are simply capable
                    models, because input pixel generally do not have only                       and equalization.                   of being implemented. Simple
                    a single output pixel  irreversible process                                  Exact graphic rendition in all      mathematical modelling,
                                                                                                 scales.                             because all elements have a
                                                                                                 Inquiry, actualization and          simple, uniform form.
                                                                                                 generalization of situation         Many data available.
                                                                                                 information and attributes.

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J. Fürst                                                                            53                                                                SS
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             Vector versus raster data structures                                        Data exchange, standardization
             Vector data structures               Raster data structures                   De-facto-standards for exchange of geometry and
             Disadvantages                        Disadvantages                            attribute information
             Complicated data structures.         Large data sets.                         Topology is not so common
             Intersection and overlay are CPU     In the case of rough resolution
             time consuming.                                                               Meta data
                                                  significant information loss.
             Representation and printout can      Unattractive map display when            national, European and international standards
             be very complex for high quality     rough resolution.                        Open-GIS Consortium (OGC): Interoperability of GIS
             printing.                            Coordinate transformations are
             Spatial analysis within primitives   complex and cause information
             is impossible, since they are        loss (irreversibly).
             regarded as homogeneous.
             Simulation models for interaction
             processes (e.g. hydrologic
             models) between elements are
             more difficult than with rasters,
             because each spatial unit
             exhibits different forms

                                                                                    55                                                               56

             Summary                                                                     Summary

                Data structures should represent spatial phenomena                         Raster data structures: generally grid of square cells,
                completely and clearly and support efficient analysis                      aligned with coordinate axes
                Discrete primitives for entities and continuous fields                     Images are special raster data sets with high
                Topology: Relationship between entities. Arc-node                          resolution
                topology supports connectivity, definition of areas and                    Thematic attributes describe „what“ an object is
                connectivity                                                               (semantics)
                Vector-GIS generally implement a layer concept with                        Thematic hierarchies can be modelled by a layer or a
                basic elements of points, lines, networks or polygons                      tree structure
                TIN is a vector data structure for continuous fields                       DBMS for robust storage of geo-data
                Object oriented data structures encapsulate data                           Adherence to national and international standards for
                objects together with methods for their behavour.                          exchange of geo-data between different systems and

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J. Fürst                                                                                                                                           SS 2007

                                                                                  Learning objectives

                                                                                    In this section you will learn:
            Coordinate Systems and Map                                              • how to clearly define the position of a point on the earth
            Projections                                                               surface,
                                                                                    • when it is important to take care of an appropriate map
            Josef Fürst                                                             • how to achieve a common projection for data from
                                                                                      different sources
                                                                                    • which type of projection meets the requirements of an

                                                                              3                                                                    4

             Outline                                                              Introduction
                Introduction                                                        Coordinate system: reference system for geographic
                Georeferencing                                                      location  Georeferencing
                 • Latitude and longitude
                                                                                    Map projection: Mapping of 3D earth surface to plane
                 • The shape of the earth
                 • Indication of height
                 • Geodetic reference systems
                Map projections
                 • Properties of map projections
                 • Classes of projections
                 • Aspect
                 • Naming of projections
                 • Selecting a suitable map projection
                 • Examples of important projections and coordinate systems
                 • Conversion of geographic coordinates

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J. Fürst                                                                                             5                                                                 SS 2007
             Georeferencing                                                                              The shape of the earth

                Longitude            and latitude                                                          Model plane: survey by theodolites, whose vertical
                  • Angle from equator: latitude                                                           axes are defined by a bubble level      trigonometry in
                  • Angle east of Greenwich: longitude                                                     a plane
                Coordinate systems are based on agreements                                                 From the sphere to an ellipsoid of rotation (spheroid)
                Coordinates relative to a „model“ of the earth                                             • Polar flattening. Meridians are ellipses   ellipsoid of
                Heights must refer to the irregular         N                                                rotation (spheroid).

                                                                                                           • Ellipticity f :

                field of gravitation

                                                                      re e n
                                                                                                                  a b
                                                                                                               f          1 / 298
                                                                                                           Problems due to gravitation field

                                                              Null-Me rid ia n G
                                                                                                           • Ellipsoid of rotation is not an exact iso-surface of
                                                                                                             gravitation; therefore deviation between coordinates
                                                                                                             from triangulation and astronomically (GPS) determined


                                                                                                     7                                                                 8
                                                                                             o                                                              Ge
             The shape of the earth                                                                      The shape of the earth

                the geoid: the „true“ shape of the earth                                                   plain, sphere, ellipsoid, geoid?
                  • Due to irregular distribution of masses within earth the                               •   Local surveys     plane trigonometry
                    geoid is irregular                                                                     •   Navigation     earth model „sphere“ .
                  • Geoid is only approximated ellipsoid of rotation                                       •   National surveys     ellipsoid of rotation
                  • Local fit of ellipsoids                                                                •   Geodetic high precision reference surveys or
                                                                                                               investigation of changes of the earth‘s body consider
                                       N                                                                       undulation of geoid



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                                                                                                                                                                        10 2007
                                                                                     o                                                                     Ge
             Heights                                                                                     Geodetic reference systems

                  Very important for hydrological applications                                             geodetic reference system: set of all theoretical
                  Height above ellipsoid h, height above geoid H, geoid                                    conventions to define a coordinate system for
                  undulation N                                                                             geodetic purposes. Reference surface (ellipsoid +
                  Heights required relativ to level (level instrument!)                                    rules for handling gedodetic measurements).
                                                                                                           Datum: set of parameters defining a coordinate
                  Erdoberfläche                                    P                                       system, and a set of control points whose geometric
                                                                                                           relationships are known, either through measurement
                     Ellipsoid                                                                             or calculation: origin, direction of axis, reference point
                                                         h H                                               for elevations
                     Geoid                                                                                 Bearing of ellipsoid in the earth usually defined by
                                                               N                                           datum point.

                                                                                                    11                                                                  12
                                                                                     o                                                                     Ge
             Geodetic reference systems                                                                  Geodetic reference systems
             Geodätische Referenzsysteme in Europa (nach Bauer, 2003)                                      Reference network: geodetic implementation of
             La                 Lag
                                  g               Hög
                                                    h                                                      reference system. Computation of coordinates and
                              Ell    tue Da
                                      La s
                                       pg m
                                       gu  u
                                           t                               k Hö
                                                                           t    m
             Frankreich      Clarke 1880         Pantheon            Marseille       Normalhöhe            heights of given points by means of geodetic surveys
             Belgien        Hayford 1924           Ukkel             Ostende        orthometrisch
             Niederlande     Bessel 1841       Amersfoort           Amsterdam       orthometrisch
                                                                                                           Usually „grown“ over long time      not free of
             Polen         Krassowski 1942       Pulkowo             Kronstadt       Normalhöhe            contradiction. Unique conversion between coordinate
             Österreich      Bessel 1841      Hermannskogel            Triest       orthometrisch
             Schweiz         Bessel 1841           Bern              Marseille      orthometrisch
                                                                                                           system, e.g. GPS, to e.g., Gauss-Krüger not possible.
             Italien        Hayford 1924           Rom             Genua; Catania   orthometrisch          Fit by reference points into reference network.
             Spanien        Hayford 1924     Potsdam (ED 50)          Alicante      orthometrisch
             Portugal        Bessel 1841         Lissabon             Cacais        orthometrisch          Austrian 3D geodetic reference field: 57.000
             Deutschland     Bessel 1841        Rauenberg           Amsterdam        Normalhöhe            triangulation points and 263.000 additional points,
                           Krassowski 1942       Pulkowo
                               GRS 80           (ETRS 89)                                                  average distance 400 to 1.500 m

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                                                                                                                                                       14 2007
             Map projections                                               Properties of map projections

                Properties of map projections                                Conformal projections
                Projection types (class)                                     • Preserve local shape            graticule lines on globe are
                aspect                                                         perpendicular
                Naming of projections                                        Equal-area projections
                Choice of appropriate projection                             • Preserve area of features                   angle and/or scale may be
                Examples of important projections
                                                                             Equidistant projections
                                                                             • Preserve distances between certain points; scale is not
                                                                               maintained correctly on an entire map
                                                                             True-direction projections
                                                                             • True-direction or azimutal projections map great-circles
                                                                               through the center point as straight lines

                                                                      15                                                                               16
                                                           s               Type of projection:                                             p
             Type of projection
                                                                           conic projections
                Projection onto geometric surfaces (plane, cone,             Tangent at standard parallel
                cylinder), which can be flattened by unrolling
                Not just pure „optical“ projection, but rather
                mathematical expressions which preserve the desired

                                                                             Secant conic projections (2 standard parallels)

                                                                                                         1. Schnittkreis

                                                                                                       2. Schnittkreis

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J. Fürst                                                                           17                                                           SS
                                                                                                                                               18 2007
             Type of projection:                                             p
                                                                            Ma          Type of projection:                                r

             cylindrical projections                                                    planar (azimuthal) projections
                Tangent or secant                                                         Tangent or secant
                Mercator projection, touches at equator                                   polar, equatorial or oblique
                Transverse Mercator projection touches at meridian




                                                                                   19                                                          20
                                                                             s                                                            Ma
             Aspect                                                                     Naming of projections
                                        cone                    cylinder   plane
                                                                                          Identified by giving:
                                                                                          • class,
                                                                                          • aspect,
                                                                                          • property.
                     normal                                                               Specific properties:
                                                                                          • name of originator,
                                                                                          • nature of any modifications.
                                                                                          E.g. topographic overview map 1:500.000: normal
                                                                                          secant conformal conic projection (LAMBERT) with
                                                                                          standard parallels 46° and 49° N latitude


816.347 GIS in Hydrology and Water Management                                                                                                       34
J. Fürst                                                                          21                                                                                                                       SS
                                                                                                                                                                                                          22 2007
                                                                         s             Examples of important map                                                                                      p
             Selecting a suitable map projection
                   Considerations                                                       UTM (Universal Transverse Mercator) System
                    • How can results be best presented on a map?                        • Gauß-Krüger version of transverse Mercator projection.
                    • For analysis in GIS, all maps must have a common                   • For cartography between 84° N and 80° S.
                      reference                                                          • Austria in UTM zone 33:
                    • To be able to quantify areas, lengths, etc. the
                      respective accuracy must be determined
                                                                                                         10°         11°       12°     13°     14°           15°      16°      17°
                   Rules of thumb                                                                   100000         200000       300000     400000           500000      600000

                    • Errors and distortions increase from the origin of the                                                                                                               49°
                                                                                          5400000                                                                                          5400000
                      projection towards its edges
                    • In tropical areas    cylindrical projections                           48°
                                                                                          5300000                                                                                          5300000
                    • In temperate latitudes     conic projections
                    • Polar regions     planar (azimuthal) projections
                   Topographic maps: conformal projections                                5200000                                                                                          5200000

                                                                                                    100000         200000       300000       400000         500000      600000
                                                                                                       10°         11°       12°       13°       14°         15°       16°     17°

                                                                                  23                                                                                                                      24
             Examples of important map                                   p
                                                                        Ma             Examples of important map                                                                                      s

             projections                                                               projections
                   WGS84                                                                Lambert conformal conic projection
                    • Measurements by GPS (Global Positioning System)                    • Used frequently for overview maps
                    • Approximate conversion of GPS coordinates into                     • Austria 1:500.000: standard parallels 46° and 49° N,
                      national system using local parameters; fit into national            central meridian 13° 20’. origin 47° 30’ N und 13° 20’ E,
                      system by reference points                                           „false“ coordinates (400.000, 400.000)
                                            zMGI                                                         10°         11°      12°     13°      14°         15°     16°     17°
                                                                                                               200000       300000      400000         500000     600000         700000
                                    zWGS           Bessel Ellipsoid                        600000                                                                                     600000
                                                                                              49°                                                                                    49°

                                                                                           500000                                                                                    500000

                                             vx,vy,vz                                         48°                                                                                    48°

                                                                yMGI                       400000                                                                                    400000

                                                                                              47°                                                                                    47°
                                                         yWGS      Ry
                   xWGS                                                                    300000                                                                                    300000

              Rx                                                                                               200000       300000      400000         500000     600000      700000
                          WGS84 Ellipsoid                                                              10°         11°       12°      13°        14°        15°     16°      17°

816.347 GIS in Hydrology and Water Management                                                                                                                                                                  35
J. Fürst                                                                                                                                                                                                       25                                                          SS
                                                                                                                                                                                                                                                                          26 2007
             Projections of the world                                                                                                                                                                               Summary

                 Geogr. coordinates                                                                                                                                                                                  Coordinates for georeference, map projections for
                                                                                                                                 10°       11°    12°      13°       14°        15°     16°    17°

                90°                                                                                              90°
                60°                                                                                              60°      49°                                                                        49°
                                                                                                                                                                                                                     According to requirements and size of study area,
                30°                                                                                              30°
                                                                                                                          48°                                                                        48°             earth‘s shape is modelled as a plane, sphere,
                 0°                                                                                              0°

                30°                                                                                              30°      47°                                                                        47°
                                                                                                                                                                                                                     ellipsoid of rotation or geoid
                60°                                                                                              60°                                                                                                 National coordinate systems are based on reference
                                                                                                                          46°                                                                        46°
                90°                                                                                              90°
                                                                                                                                 10°       11°    12°      13°       14°        15°     16°    17°
                 Mollweide (equal area)                                                                                                                                                                              Position related to ellipsoid
                              -15000000   -10000000   -5000000   0   5000000   10000000   15000000                                     -200000   -100000         0         100000     200000   300000                Gravitation field to be considered for heights
                                                                                                                           49°                                                                       49°
                                                                                                                                                                                                                     Distortions due to projection: a projection cannot


                                                                                                                       5700000                                                                       5700000

                                                                                                                           48°                                                                       48°
                                                                                                                                                                                                                     maintain conformity, equal area, equidistance AND


                                                                                                                       5600000                                                                       5600000
                                                                                                                                                                                                                     true direction at the same time

                                                                                                                           47°                                                                       47°             important: UTM, Gauß-Krüger, Lambert conformal


                                                                                                                       5500000                                                                       5500000
                                                                                                                                                                                                                     conic projection
                              -15000000   -10000000   -5000000   0   5000000   10000000   15000000                                     -200000   -100000         0         100000     200000   300000

816.347 GIS in Hydrology and Water Management                                                                                                                                                                                                                                  36
J. Fürst                                                                                                                                  SS 2007

                                                                           Learning objectives

                                                                             In this section you will learn:
                                                                             • how thematic overlays work,
            Analysis of Spatial Data
                                                                             • overview of the diversity of spatial analysis tools and
                                                                             • overview of methods to query and select by attributes
                                                                               and spatial criteria to serve as a basis for GIS based
            Josef Fürst                                                        decision support.


                                                                       3                                                                  4

             Outline                                                       Introduction

                Introduction                                                 Most important functionality of GIS
                Geometric overlay                                            GIS data basis as a model of reality
                Analysis in attribute space                                  „single layer“ analyses
                Integrated analysis of spatial and thematic data             „multiple layers“ analyses
                Raster-GIS functions                                         Useful distinction from a technical viewpoint:
                Example: Delineation of hydrologically similar areas         • Funktions for analysis in attribute space
                Summary                                                      • Funktions for analysis by spatial (topological) criteria

816.347 GIS in Hydrology and Water Management                                                                                                 37
J. Fürst                                                              5                                                                              SS 2007

             Geometric overlay                                            Geometric overlay

                Statements about a location combining information           Topological fragmentation
                from 2 or more thematic maps      „overlay“ of 2 or
                more maps
                requires common spatial reference
                In raster-GIS automatically met
                Geometric overlay (intersection) in vector-GIS
                required overlay operators

                                                                      7                                                                              8
                                                                                                                             Analysis in attribute
             Analysis in attribute space                                  Query                                              space

                query,                                                      Selection of attribute data, without changes in
                generalisation,                                             database
                calculation.                                                SQL (Structured Query Language)
                                                                            SELECT KENNUNG, STATIONSNAME, X_KOORDINATE, Y_KOORDINATE,
                                                                            FROM HEADER_HYDRO
                                                                            WHERE MESSVARIABLE = ´GRUNDWASSERSTAND´ AND MESSGERAET =
                                                                            ArcView 3.x:

816.347 GIS in Hydrology and Water Management                                                                                                            38
J. Fürst                                                                                         9                                                                               SS
                                                                                                                                                                                10 2007
                                                                         Analysis in attribute                                                          Analysis in attribute
             Generalisation                                              space                        Generalisation                                    space

                Classification of data by user defined rules, without                                   Generalisation by classifying an attribute
                change of existing attributes
                  • Clearer view of inherent patterns
                  •   Weekly and monthly precipitation depths,
                  •   Soil classification by hydrological criteria,
                  •   Classification of slopes for stability analysis,
                  •   Hydrological Response Units (HRU)

                                                                                                 11                                                                             12
                                                                         Analysis in attribute        Integrated analysis of spatial and
             Calculations                                                space
                                                                                                      thematic data
                Operations:                                                                             The focus of GIS
                  • arithmetic,                                                                         Power of analytical functions and software
                  • mathematical (funktions) and                                                        architecture varies
                  • logical (binary)                                                                    • Wide range from specialised modules for catchment
                E.g.: Amount of groundwater = Thickness x porosity                                        analysís (e.g., WMS) to libraries of elementary general
                SQL DBMS like Oracle or MS Access such attributes                                         purpose spatial operators
                are commonly stored in a „view“ or „query“

816.347 GIS in Hydrology and Water Management                                                                                                                                        39
J. Fürst                                                                                 13                                                                               SS
                                                                                                                                                                         14 2007
                                                                   Integrated analysis                                                             Integrated analysis
             Selection, classification and measuring                                          Classification

                combined spatial and attribute based selection                                  (Re-)assignment of thematic attributes
                E.g.: Select features of active themes that Are                                 Examples:
                completely within the selected features of                                       • Elevation zones from DEM
                Grenzen3.shp                                                                     • Re-classification of a soil map by hydrological criteria
                                                                                                 • Scale-dependent reduction of number of attribute
                                                                                                   values, e.g. in a map of land cover

                                                                                         15                                                                              16
                                                                   Integrated analysis                                                             Integrated analysis
             Measure                                                                          Overlays (Intersection)

                Assess numbers, distances, lengths, areas, volumes                              M:N relationship between entities of 2 maps with
                  • Many of these are automatically maintained in GIS                           different geometrical basis
                    (area and perimeter of polygons, length of lines),                          1:N relationship between a polygon and ist attributes
                  • Sometimes elaborate procedures (e.g. travel time as a                       by geometric-topological intersection
                    function of road conditions, vehicle and current traffic)                   After intersection analysis is done in a single layer
                                                                                                 • arithmetic (addition, multiplication, ...) and
                                                                                                 • logical (AND, OR, XOR) operations as well as
                                                                                                 • Application of conditions (rules)

816.347 GIS in Hydrology and Water Management                                                                                                                                 40
J. Fürst                                                                                                      17                                                                                                       SS
                                                                                                                                                                                                                      18 2007
                                                                                        Integrated analysis                                                                                     Integrated analysis
             Overlays (Intersection)                                                                               Overlays (Intersection)

                Example of arithmetic overlay                                                                        Example of a logical overlay
                    1                                                                                                   1
                                                                                    2                                                                                                   2
                             2                                                                                                   2
                                                                 1                                                                                                   1

                                       3                                        3                                                          3                                        3

                 Durchwurzelungstiefe [cm]                 Bodenfeuchte [%]                                          Durchwurzelungstiefe [cm]                 Bodenfeuchte [%]
                 WTID WTIEFE                               BFID BFEUCHTE                                             WTID WTIEFE                               BFID BFEUCHTE
                 1      50                                 1       23                                                1      50                                 1       23
                 2      75                                 3       34                                                2      75                                 3       34
                 3      89                                 2       18                                                3      89                                 2       18

                                                 Intersect                                                                                           Intersect
                                                    Pflanzenverfügbares Wasser [mm]                                      1/1               2/2          Tiefe Durchwurzelung, geringe Feuchte
                     1/1               2/2
                                                    PWASSER = WTIEFE * BFEUCHTE / 10                                                                    WTIEFE > 80 AND BFEUCHTE < 20
                           2/1                      WTID WTIEFE BFID BFEUCHTE PWASSER                                          2/1                      WTID WTIEFE BFID BFEUCHTE
                                                    1      50    1      23      115                                                                     1      50    1      23
                                                    2      75    1      23      173                                                            3/3      2      75    1      23
                           3/1             3/3                                                                                 3/1                      2      75    2      18
                                                    2      75    2      18      135
                                                    3      89    1      23      205                                                                     3      89    1      23
                                 3/2                                                                                                 3/2                3      89    3      34
                                                    3      89    3      34      303
                                                    3      89    2      18      160                                                                     3      89    2      18

                                                                                                              19                                                                                                      20
                                                                                        Integrated analysis                                                                                     Integrated analysis
             Overlays (Intersection)                                                                               Overlays (Intersection)

                Point in Polygon overlay by Spatial Join in ArcView                                                  Line in Polygon overlay: rivers are assigned the surrounding
                3.x: groundwater sites receive an attribute „Land cover“                                             land cover by INTERSECT of the maps „Rivers“ and „Land
                (Bedeckung) by spatial join with the map „Land cover“                                                cover“

816.347 GIS in Hydrology and Water Management                                                                                                                                                                              41
J. Fürst                                                                                                 21                                                                            SS
                                                                                                                                                                                      22 2007
                                                                                   Integrated analysis                                                          Integrated analysis
             Surface operations                                                                               Connectivity

                neighbourhood of a point is included in the evaluation                                          Entities with common properties AND spatial
                for this point                                                                                  connection
                Generally a „smooth“ surface is assumed                                                         • Contiguity
                  •   Topographic functions (slope, aspect, relief),                                            • Proximity: based on measures of distance, including
                  •   illumination (e.g. hillshading),                                                            time, cost, etc. E.g. buffer zones, Thiessen polygons,
                  •   Pseudo-3D displays (Perspective) and                                                        flow times).
                  •   Interpolation.                                                                            • Spread: e.g. floods, pollutants.
                                                                                                                • Seek: optimal paths, according to decision rules,
                                                                                                                • Network functions: utilities, drainage network.

                                                                                                         23                                                                           24
                                                                                   Integrated analysis                                                          Integrated analysis
             Connectivity                                                                                     Connectivity

                contiguity:                                                                                     proximity:
                  • E.g: nature reserve should contain forest, swamp and                                        • E.g.: buffer zones near rivers: width depends on land
                    rivers, min. size 400 km2 and nowhere narrower than                                           cover
                    10 km.
                      Bodenbedeckung                    Zusammenhängende Flächen

                             Wald               Acker

                             Sumpf              Fluss

816.347 GIS in Hydrology and Water Management                                                                                                                                              42
J. Fürst                                                                                 25                                                                                                                    SS
                                                                                                                                                                                                              26 2007
                                                                   Integrated analysis                                                                                 Integrated analysis
             Connectivity                                                                     Connectivity

                proximity:                                                                      Spread (flood, noise, pollutants in groundwater)
                  • E.g: Thiessen-Polygons: raster based    assign                              • in GIS usually only simplified solutions
                    proximity, vector based   line of symmetry                                  Seek
                                                                                                • Find optimal path using decision rules                                                                  1
                                                                                                                                                                                   1          2
                                                                                                Network functions (roads,                  1
                                                                                                                                       1                1
                                                                                                sewers, utilities, rivers)                     2                1 1                    W          1

                                                                                                                                                       2        2
                                                                                                • Movement of resources



                                                                                                                                                            3          1       1
                                                                                                                                                         is t

                                                                                                • Strahler order
                                                                                                                                                                3              2



                                                                                                                                                            Donau 7

                                                                                         27                                                                                                                   28
                                                                                              Example: Delineation of hydrological
             Raster-GIS functions
                                                                                              response units
                Local functions                                                                 Semi-distributed conceptual models with HRU
                  • Only one cell, neighbouring cells do not influence result                   concept (e.g. PRMS)
                Focal functions                                                                 Important steps:
                  • Result for a cell is based on neighbourhood cells (linear                   • Selection of input data: 5 layers, DEM (slope, aspect),
                    filter, mean, median, standard deviation )                                    land use, soil, geology
                Zonal functions                                                                 • classification input data into small number of categories
                  • Evaluated for a zone, i.e. for all cells with a common                        (3-6).
                    value                                                                       • Overlay of input layers.
                Global functions                                                                • Reduction of the resulting number of unique attribute
                  • Calculations for the whole grid (distances, delineation of                    combinations (HRU) by analysis and classification in
                    catchments)                                                                   DBMS

816.347 GIS in Hydrology and Water Management                                                                                                                                                                      43
J. Fürst                                                                                                                  29                                                               SS
                                                                                                                                                                                          30 2007

             Water balance of the Danube basin                                                                                 Summary
                                                                                       11 Klassen
                HRU using                                                                                                       Analysis of spatial data is the most important function
                DEM (250 m resolution),                                                                                         of GIS
                maps of land cover and                                                                                          Single-layer analysis is done within 1 layer
                                                           Klassifikation                                Klassifikation         Multi-layer analysis
                hydrological sub-basins                     3 Klassen                                     3 Klassen

                                                                                       Bodenbedeckung                            • Transform into single-layer problem by geometric-
                                                                                       Wald, Gras,
                                                                                                                                   topological intersection   1:M relationship between
                                                                                                                                   object and attributes.
                                                                                                                                Analyses in attribute space include query,
                                                                                   Overlay                                      generalisation and calculations based on the
                                                Zonen (HRU) für Bilanzmodell
                                                                                                                                attributes only
                                                Overlay aus klassifiziertem DHM,
                                                Bodenbedeckung, Einzugs-                                                        Integrated analysis of spatial and attribut data
                                                                                                                                involves attributes, location and topology
                                                                                                                                selection, classification and measure, overlay
                                                                                                                                (intersection), surface operations, analysis of spatial

816.347 GIS in Hydrology and Water Management                                                                                                                                                  44
J. Fürst                                                                                                         SS 2007

                                                        Learning objectives

                                                          In this section you will learn:
            Overview of GIS Software and                  • Overview of the architecture and categories of GIS
            Products                                        software,
                                                          • Criteria for selection of a GIS and
                                                          • Overview of available geodata and services
            Josef Fürst


                                                    3                                                            4

             Outline                                    Introduction

                Introduction                              Market is almost overwhelming
                GIS technology                            On one side a concentration on few dominant
                Avaliability of geodata                   products is observed,
                Services                                  But also many new products (add-ons)
                Summary                                   Up-to-date information on WWW

816.347 GIS in Hydrology and Water Management                                                                        45
J. Fürst                                                                       5                                                                   SS 2007

             GIS technology                                                        GIS technology

                Development of GIS technology is closely related to                  System categories and how they work together
                general development of IT
                                                                                            GIS-Server / Geodaten-Server / Map Server
                Hardware: generally increased power of computers;
                esp. also peripherals for data acquisition and                                               Netzwerk
                                                                                                   Desktop-GIS      Web-GIS          GIS-
                     Benutzer-              Benutzer-          Benutzer-                                                          Anwendungen
                    schnittstelle          schnittstelle      schnittstelle

                 Datenverwaltung         Datenverwaltung    Datenverwaltung

                Integrierte Anwendung   Geodatenserver     Anwendungs-Server

                                                                               7                                                                   8

             GIS technology                                                        Availability of geodata

                                                                                     Data are the most important part of GIS
                                                                                      • „lifetime“of hardware 3-5 y, software 10 y, many basic
                                                                                        data 50 (?) y
                                                                                     Increasing availability of geodata
                                                                                      • Topographic maps, road data, digital orthophotos,
                                                                                        demographic data
                                                                                      • New techniques of acquisition like mobile GPS-based
                                                                                        mapping, digitale photogrammetry and satellite and
                                                                                        airborne remote sensing
                                                                                      • EU initiatives, ESDI

816.347 GIS in Hydrology and Water Management                                                                                                          46
J. Fürst                                                                                                               9                                                                SS
                                                                                                                                                                                       10 2007

             Availability of geodata                                                                                        Services
                  • Hydrological atlasses                                                                                     Software development, adaptation, maintenance
                  • Availability of digital drainage networks in Europe                                                       Development of interfaces, digitizing, scanning,
                                                                                 Legend:                                      vektorisation, data collection, database design,
                                                                                 Rivers and lakes at
                                                                                 scale 200 000 or better                      surveying, field data collection, consulting, training
                                                                                       < 50% of country area
                                                                                      > 50%                                   Data conversion, hydraulic networks, satellite image
                                                                                      100 % of country area
                                                  NOR                              0 200 400 600 800 Kilometers
                                                                                                                              processing, georeferencing, distribution of GIS data,
                                                                                   RUS                                        3D visualization, Internet-GIS
                                                  DNK            LTU
                                                                           BLR                                                Large bandwidth: surveyors, software companies,
                                  IRL                                                                      KAZ
                                        GBR     NLD            POL
                                              BEL DEU                            UKR
                                                                                                                              consulting firms in water landscape planning
                                               LUX        CZE
                                                                             MDA                                              externalised GIS-services
                                                 CHE          HUN
                                          FRA                        ROM                               GEO AZE
                                                              BIH SRB
                                                MCO     ITA    MON    BGR

                                                                     ALB                      TUR
                          PRT     ESP                                  GRC
                                                                                           CYP LBN
                                                 TUN                                             JOR



                GIS software is the foundation of GIS application.
                Three layer architecture (data management, tools and
                user interface) facilitates division of work
                Current development towards distributed GIS
                Increasing availability of GIS based data. Many
                datasets free of cost (or low cost) for regional
                Market for GIS software, geodata and a wide range of

816.347 GIS in Hydrology and Water Management                                                                                                                                               47

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