GIS lab by cbchisanga8

VIEWS: 70 PAGES: 15

									SUBJECT: Geographical Information System (GIS) Laboratory
              (Land Information System)

                            By

                 Charles Bwalya Chisanga


                    6th September 2011
                      updated write-up




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Introduction

GIS integrates hardware, software, and data for capturing, managing, analyzing, and displaying all
forms of geographically referenced information. GIS technology allows you to view, query, and
understand data in many ways. You’ll see relationships, patterns, and trends in the form of GIS-
based maps, reports, and charts. GIS helps you answer questions and solve problems. When viewed
 in the context of geography, your data is quickly understood and easily shared. GIS technology can
be integrated into any enterprise information system framework.

GIS technology integrates common database operations such as query and statistical analysis with
the unique visualization and geographic analysis benefits offered by maps. These abilities
distinguish GIS from other information systems and make it valuable to a wide range of public and
private enterprises for explaining events, predicting outcomes, and planning strategies. Map making
and geographic analysis are not new, but a GIS performs these tasks faster and with more
sophistication than do traditional manual methods.

GIS (Geographic Information System): computer information system that can input, store,
manipulate, analyze, and display geographically referenced (spatial) data to support decision
making processes. It also involves the mapping and analyzing things that exist and events that
happen on earth. GIS technology integrates common database operations such as query and
statistical analysis with the unique visualization and geographic analysis. These abilities distinguish
GIS from other information systems and make it valuable to a wide range of public and private
enterprises for explaining events, predicting outcomes, and planning strategies.

A geographic information system (GIS) is a computer-based tool for mapping and analyzing things
that exist and events that happen on earth. GIS technology integrates common database operations
such as query and statistical analysis with the unique visualization and geographic analysis benefits
offered by maps. These abilities distinguish GIS from other information systems and make it
valuable to a wide range of public and private enterprises for explaining events, predicting
outcomes, and planning strategies (ESRI 1997).

GIS as a single, well-defined, integrated computer system. However, this is not always the case. A
GIS can be made up of a variety of software and hardware tools. The important factor is the level of
integration of these tools to provide a smoothly operating, fully functional geographic data
processing environment. In general, a GIS provides facilities for data capture, data management,
data manipulation and analysis, and the presentation of results in both graphic and report form, with
a particular emphasis upon preserving and utilizing inherent characteristics of spatial data.

A GIS is comprised of hardware, software, data, humans, and a set of organizational protocols.
These components must be well integrated for effective use of GIS, and the development and
integration of these components is an iterative, ongoing process. The selection and purchase of
hardware and software is often the easiest and quickest step in the development of a GIS. Data
collection and organization, personnel development, and the establishment of protocols for GIS use
are often more difficult and time-consuming endeavors.

A geographic information system, commonly referred to as a GIS, is an integrated set of hardware
and software tools used for the manipulation and management of digital spatial (geographic) and
related attribute data.



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Setting up a GIS laboratory

GIS Definition:
     A system for capturing, storing, checking, manipulating, analyzing and displaying data
      which are spatially referenced to the Earth.
      Any manual or computer based set of procedures used to store and manipulate
      geographically referenced data (Runoff, 1989)
     A database system in which most of the data are spatially indexed, and upon which a set of
      procedures operated in order to answer queries about spatial entities in the database.
      (Smith, 1987)
     A GIS is a collection of hardware, software, geographic data, and personnel designed to
      create, store, edit, manipulate, analyze and display geographically referenced information.
     "GIS is a powerful set of tools for collecting, storing, retrieving at will, transform and
      displaying spatial data from the real world", (Burrough, 1986)

In general, people use a GIS for four main purposes: data creation, data display, analysis, and output
(Four components of any GIS: input; storage/retrieval; analysis; display). Objects can be
displayed according to the data in your database. GIS analysis tools allow you to do things like find
out how far your best customers travel to visit your store, which land parcels are within a flood
zone, and which soil type is best for growing a particular crop. Output options include cartographic-
quality maps as well as reports, lists, and graphs.

A GIS has four main functional subsystems. These are:

 a data input subsystem;
 a data storage and retrieval subsystem;
 a data manipulation and analysis subsystem; and
 a data output and display subsystem.

Data Input
A data input subsystem allows the user to capture, collect, and transform spatial and thematic data
into digital form. The data inputs are usually derived from a combination of hard copy maps, aerial
photographs, remotely sensed images, reports, survey documents, etc.

Data Storage and Retrieval
The data storage and retrieval subsystem organizes the data, spatial and attribute, in a form which
permits it to be quickly retrieved by the user for analysis, and permits rapid and accurate updates to
be made to the database. This component usually involves use of a database management system
(DBMS) for maintaining attribute data. Spatial data is usually encoded and maintained in a
proprietary file format.

Data Manipulation and Analysis
The data manipulation and analysis subsystem allows the user to define and execute spatial and
attribute procedures to generate derived information. This subsystem is commonly thought of as the
heart of a GIS, and usually distinguishes it from other database information systems and computer-
aided drafting (CAD) systems.

Data Output
The data output subsystem allows the user to generate graphic displays, normally maps, and


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tabular reports representing derived information products.

The critical function for a GIS is, by design, the analysis of spatial data.

It is important to understand that the GIS is not a new invention. In fact, geographic information
processing has a rich history in a variety of disciplines. In particular, natural resource specialists and
environmental scientists have been actively processing geographic data and promoting their
techniques since the 1960's.

GIS Activities
Activities related with Spatial Data Capturing
Geometric location of geographic features (that is location of point, line, or polygon). Attribute data
(a characteristic of a geographic feature described by numbers., or characters stored in a tabular
format and linked to the geographic features). Data types used in GIS are; geographical and
attribute data in association with each other. Generally, the geographical data represented as points,
lines or polygons and attributes are linked to it.

Stages of spatial data capturing
Scanning of Source Maps - It is a process of converting paper/cloth map on to the digital media.
Map Preparation (The scanned Maps will be scaled on the basis of the dimensions given by the
clients through rubber sheet process after which on screen digitization will be done to convert
raster drawings (maps) to vector format through CAD systems such as AutoCAD Map.
Digitization/vectorisation is the process of converting graphical information into a digital format.

The Map is digitized into different layers, or themes. There is one layer for each set of geographic
features or phenomena for which attribute information’s if available will be recorded. For example,
outer boundary, road, plots, etc. and each will be stored as a separate spatial data sources, rather
than trying to store them all together in one.

Data Linkage: The next important activity after spatial and attribute data capturing is the process of
linking the two data sets. So far these databases are in different environments and need to be
integrated for mapping related queries. For integration of data there should be a unique field in both
spatial as well as attributes data sets.

Map Integration: The Application for integration purpose can be developed in Map Object
Software through visual basic where both maps, its attribute data and external data can be visualized
at a time and all the GIS related mapping. Operations i.e. query analysis; thematic mapping,
zooming, panning, addition and deletion of layer etc will be possible through this application.

GIS is an integration of five (5) basic components: hardware, software, people, data and analysis
(procedures or methods).




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Geographic information system(GIS) is
 an organized collection of ...
  • Data,
  • Software,
  • Hardware,
  • People,
  • Procedures &
  • Network,
designed to ...
  • capture,
  • store,
  • manipulate,
  • update,
  • analyze &
  • display
spatial data



                                       Basic components of GIS



   1. Hardware
   A fast computer, large data storage capacities, and a high-quality, large display form the
   hardware foundation of most GIS. A fast computer is required because spatial analyzes are often
   applied over large areas and/or at high spatial resolutions. Calculations often have to be repeated
   over tens of millions of times, corresponding to each space we are analyzing in our geographical
   analysis. Even simple operations may take substantial time if sufficient computing capabilities
   are not present, and complex operations can be unbearably long-running.

   Hardware is the computer on which a GIS operates. Today, GIS software runs on a wide range
   of hardware types, from centralized computer servers to desktop computers used in stand-alone
   or networked configurations. The hardware includes: Computer, Scanners, Plotters/Printer,
   Digitizers, Servers/Workstations/Desktops, Local Area Network (LAN)




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              GIS are typically used with a number of general purpose and specialized hardware components.




                                          Functions commonly provided by GIS software



    2. Software
GIS software provides the functions and tools needed to store, analyze, and display geographic
information. The selection and purchase of hardware and software is often the easiest and quickest step in
the development of a GIS.

    Key software components are:

          Tools for the input and manipulation of geographic information;
       A database management system (DBMS)


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   Tools that support geographic query, analysis, and visualization;
A graphical user interface (GUI) for easy access to tools

Loading/Extracting:
     shp2pgsql
     shp2pgsql-gui
     pgsql2shp
     SPIT (Shapefile to PostGIS Import Tool)
     ogr2ogr
     osm2pgsql
     dxf2postgis
     safe FME Desktop
     Translator/Converter
Proprietary software:
     ArcGIS Desktop software (ESRI, Inc - ArcGIS)
     MapInfo Professional v10+ & MapBasic
     CAD Software & PostGIS (AutoDesk - AutoCAD Map)
     Autodesk MapGuide Enterprise 2009 Server
     ERDAS (Earth Resources Data Analysis System)
     PCI Geomatica
     Maniford GIS (www.manifold.net)
     Cadcorp SIS
     GeoMedia (Intergraph)
     Safe FME (FME is the dominant technology for spatial data transformation)
     ENVI
     Microimages TNTmips
     Idris - provides both image processing and GIS functions
     Microsoft Visual Basic 2005/2008/2010 (Microsoft Visual Studio)
     Trimble eCognition
Open source software:
     GRASS GIS (Geographical Resources Analysis Support System – raster/vector GIS)
     Quantum GIS (Graphic data viewers for GRASS GIS; work with PostgreSQL
      DBMS through PostGIS package)
     Openjump (Java Unified Mapping Platform)
     Thuban (Graphic data viewers for GRASS GIS)
     uDIG
     SAGA GIS (System for Automated Geoscientific Analysis GIS)
     Ilwis (Integrated Land and Water Information System)
     Gearscape GIS
     DraftSight (open source CAD)
     BrlCAD (open source CAD)
     OrbgiGIS
     gvSIG (open GIS written in java)
     MapWindow .NET SDK
     Elshayal Smart GIS Map Editor and Surface Analysis
     ArcGIS/ArcObjects.NET
     OpenEV
     ZigGIS PostGIS connector is an ArcGIS plugin


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              PostGISViewer

        Database Server software:
             Oracle spatial (Oracle 9iR2, 10Gr2, 11G)
             Microsoft SQL server 2008
             PostgreSQL/PostGIS
             IBM DB2 Spatial Extender
             MySQL
             ESRI ArcSDE
             Geomedia on MS Access
        Web Based GIS software:
             MapGuide open source (using FDO)
             UMN/MapServer
             The GRASS GIS Server
             Mapblender
             MapQuest
             GeoServer (Java-based WFS/WMS - server)
             ESRI, Inc – ARCIMS
             MapGuide Enterprise (using FDO)
             Cadcorp GeohnoSIS
             Mapnik (C++/python library rendering – used in openStreetMap)

FME Desktop Supported applications
The power of FME Desktop can be accessed directly from within many popular spatial applications,
including:
       Autodesk Civil 3D
       Autodesk Map 3D
       Bentley Microstation
       ERDAS IMAGINE
       Esri ArcGIS
       GE Energy Smallworld
       Google Earth/Maps
       Informatica PowerCenter
       Intergraph GeoMedia Professional
       MapInfo Professional
       Microsoft SQL Server
       Oracle Spatial
       PostGIS

    3. People
GIS technology is of limited value without the people who manage the system and develop plans
for applying it to real-world problems. GIS users range from technical specialists, who design and
maintain the system to those who use it to help them perform their everyday work. The
personnel/staff will create, store, edit, manipulate, analyze and display geographically referenced
information. The identification of GIS specialists versus end users is often critical to the proper
implementation of GIS technology. Effective use of GIS requires an organization to support
various GIS activities. Most GIS also require trained personnel to use them, and a set of protocols
guiding how the GIS will be used. The institutional context determines what spatial data are

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important, how these data will be collected and used, and ensures that the results of GIS analysis are
properly interpreted and applied. GIS share a common characteristic of many powerful
technologies. If not properly used, the technology may lead to a significant waste of resources, and
may do more harm than good. The proper institutional resources are required for GIS to provide all
its potential benefits.

One important question that must be answered early is “what problem(s) are we to solve with the
GIS?” GIS add significant analytical power through the ability to measure distances and areas,
identify vicinity, analyze networks, and through the overlay and combination of different
information. Unfortunately, spatial data development is often expensive, and
effective GIS use requires specialized knowledge or training, so there is often
considerable expense in constructing and operating a GIS. Before spending this time
and money there must be a clear identification of the new questions that may be answered, or the
process, product, or service that will be improved, made more efficient, or less expensive through
the use of GIS.




GIS exist in an institutional context. Their effective use depends on a set of protocols and an integration into the data collection,
                                       analysis, decision, and action loop of an organization.

   4. Data
      Possibly the most important component of a GIS is the data. Geographic data and related
      tabular data can be collected in-house or purchased from a commercial data provider. A GIS
      will integrate spatial data with other data resources and can even use a DBMS, used by most
      organizations to organize and maintain their data, to manage spatial data.



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       A GIS can integrate spatial data with other existing data resources, often stored in a
       corporate DBMS. The integration of spatial data (often proprietary to the GIS software), and
       tabular data stored in a DBMS is a key functionality afforded by GIS.

       Geographic features (points, lines, polygons) used for visualization and analysis. Vector data
       is in form of point, line and polygon and Raster data (satellite images). Raster is a grid
       consisting of individual cells or pixels. Each cell holds a value (elevation, radiance,
       reflectance, rainfall or land use type etc). The resolution of the data is the size on the ground
       by each cell.
       Data sources – digitized and scanned maps, GPS, databases, remote sensing and aerial
       photography and field sampling of attributes.

   5. Analysis (procedures or methods)
      A successful GIS operates according to a well-designed plan and business rules, which are
      the models and operating practices unique to each organization.

       A successful GIS operates according to a well-designed implementation plan and business
       rules, which are the models and operating practices unique to each organization.
       As in all organizations dealing with sophisticated technology, new tools can only be used
       effectively if they are properly integrated into the entire business strategy and operation. To
       do this properly requires not only the necessary investments in hardware and software, but
       also in the retraining and/or hiring of personnel to utilize the new technology in the proper
       organizational context. Failure to implement your GIS without regard for a proper
       organizational commitment will result in an unsuccessful system! Many of the issues
       concerned with organizational commitment are described in Implementation Issues and
       Strategies.

It is simply not sufficient for an organization to purchase a computer with some GIS software, hire
some enthusiastic individuals and expect instant success.

GIS DATA MODELS
A GIS stores information about the world as a collection of thematic layers that can be linked
together by geography. This simple but extremely powerful and versatile concept has proven
invaluable for solving many real-world problems from tracking delivery vehicles, to recording
details of planning applications, to modeling global atmospheric circulation. The thematic layer
approach allows us to organize the complexity of the real world into a simple representation to help
facilitate our understanding of natural relationships.


GIS DATA TYPES
The basic data type in a GIS reflects traditional data found on a map. Accordingly, GIS technology
utilizes two basic types of data. These are:
Spatial data            describes the absolute and relative location of geographic features.
Attribute data          describes characteristics of the spatial features. These characteristics can
                        be quantitative and/or qualitative in nature. Attribute data is often referred
                        to as tabular data.

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SPATIAL DATA MODEL
Traditionally spatial data has been stored and presented in the form of a map. Three basic types of
spatial data models have evolved for storing geographic data digitally. These are referred to as:
 Vector;
 Raster;
 Image.

VECTOR DATA FORMATS
All spatial data models are approaches for storing the spatial location of geographic features in a
database. Vector storage implies the use of vectors (directional lines) to represent a geographic
feature. Vector data is characterized by the use of sequential points or vertices to define a linear
segment. Each vertex consists of an X coordinate and a Y coordinate.
Vector lines are often referred to as arcs and consist of a string of vertices terminated by a node. A
node is defined as a vertex that starts or ends an arc segment. Point features are defined by one
coordinate pair, a vertex. Polygonal features are defined by a set of closed coordinate pairs. In
vector representation, the storage of the vertices for each feature is important, as well as the
connectivity between features, e.g. the sharing of common vertices where features connect.




RASTER DATA MODEL
Raster data models incorporate the use of a grid-cell data structure where the geographic area is
divided into cells identified by row and column. This data structure is commonly called raster.
While the term raster implies a regularly spaced grid other tessellated data structures do exist in grid
based GIS systems. In particular, the quadtree data structure has found some acceptance as an
alternative raster data model.




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IMAGE DATA
Image data is most often used to represent graphic or pictorial data. The term image inherently
reflects a graphic representation, and in the GIS world, differs significantly from raster data. Most
often, image data is used to store remotely sensed imagery, e.g. satellite scenes or orthophotos, or
ancillary graphics such as photographs, scanned plan documents, etc. Image data is typically used in
GIS systems as background display data (if the image has been rectified and georeferenced); or as a
graphic attribute. Remote sensing software makes use of image data for image classification and
processing. Typically, this data must be converted into a raster format (and perhaps vector) to be
used analytically with the GIS.

Several different vector data models exist, however only two are commonly used in GIS data
storage.

The most popular method of retaining spatial relationships among features is to explicitly record
adjacency information in what is known as the topologic data model. Topology is a mathematical
concept that has its basis in the principles of feature adjacency and connectivity.

The topologic data structure is often referred to as an intelligent data structure because spatial
relationships between geographic features are easily derived when using them. Primarily for this
reason the topologic model is the dominant vector data structure currently used in GIS technology.
Many of the complex data analysis functions cannot effectively be undertaken without a topologic
vector data structure.
The secondary vector data structure that is common among GIS software is the computer-aided
drafting (CAD) data structure. This structure consists of listing elements, not features, defined by
strings of vertices, to define geographic features, e.g. points, lines, or areas. There is considerable
redundancy with this data model since the boundary segment between two polygons can be stored
twice, once for each feature. The CAD structure emerged from the development of computer
graphics systems without specific considerations of processing geographic features. Accordingly,
since features, e.g. polygons, are self-contained and independent, questions about the adjacency of
features can be difficult to answer. The CAD vector model lacks the definition of spatial


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relationships between features that is defined by the topologic data model.


ATTRIBUTE DATA MODEL
A separate data model is used to store and maintain attribute data for GIS software. These
data models may exist internally within the GIS software, or may be reflected in external
commercial Database Management Software (DBMS). A variety of different data models exist for
the storage and management of attribute data. The most common are:
            Tabular
            Hierarchial
            Network
            Relational
            Object Oriented
The tabular model is the manner in which most early GIS software packages stored their attribute
data. The next three models are those most commonly implemented in database management
systems (DBMS). The object oriented is newer but rapidly gaining in popularity for some
applications. A brief review of each model is provided.

GIS functionality

While creating digital and hardcopy maps has been the core GIS function over the past decade, the
emphasis is shifting towards spatial analysis and modeling. GIS functionality is rapidly evolving
and currently covers a wide range of areas, for example ;

    integration of geospatial data from various sources: projections and coordinate
     transformations, format conversions, spatial interpolation, transformations between data
     models;
    visualization and communication of digital georeferenced data in form of digital and paper
     maps, animations, virtual reality (computer cartography);
    spatial analysis: spatial query, spatial overlay (combination of spatial data to find locations
     with given properties), neighborhood operations, geostatistics and spatial statistics;
    image processing: satellite and airborne image processing, remote sensing applications;
    network analysis and optimization;
    simulation of spatial processes: socioeconomic such as transportation, urban growth,
     population migration as well as physical and biological, such as water and pollutant flow,
     ecosystem evolution, etc.

This functionality is used to solve spatial problems in almost every area of our lives. Here are a few
examples. In the area of socioeconomic applications, GIS can be used to find directions, locate a
hospital within a given distance from a school, find optimal locations for a new manufacturing
facility, design voter districts with given composition and number of voters, identify crime hot
spots in a city, select optimal evacuation routes, manage urban growth. GIS plays an important role
in conservation of natural resources and management of natural disasters, such as identification and
prevention of soil erosion risk, forest resource management, ecosystem analysis and modeling,
planning of conservation measures, flood prediction and management, pollutant modeling, etc.
GIS is also being increasingly used in agriculture, especially in the area of precision farming.




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Summary
GIS are computer-based systems that aid in the development and use of spatial data. There are many
reasons we use GIS, but most are based on a societal push, our need to more effectively and
efficiently use our resources, and a technological pull, our interest in applying new tools to
previously insoluble problems. GIS as a technology is based on geographic information science,
and is supported by the disciplines of geography, surveying, engineering, space science, computer
science, cartography, statistics, and a number of others.

GIS are most often used as decision-support tools, the effective use of GIS requires more than the
purchase of hardware and software. Trained personnel and protocols for use are required if GIS are
to be properly applied. GIS may then be incorporated in the question-collect-analyze-decide loop
when solving problems.




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PLANNING A GIS PROJECT
STEP ONE
Define problem and project goals
Consider the following questions
     What is the problem to be solved? How is it to be solved? Are there alternative ways to
        solve it using GIS? Will the data be used for other purposes?
     What are the final products of the project – reports, working maps, presentation-quality
        maps?
     Who is the intended audience of these products –the public, planners, technicians, officials
        etc
     Will the data be used for other purposes? What are the requirements for these?
Step one is important because the answers to the questions determines the scope of the project as
well as how the analysis is implemented.

STEP TWO
Develop methodology and analysis flow
Create a project database (is critical and time consuming part of the project)
    Designing the database includes identify spatial data based on the requirement of the
       analysis, determine the required feature attributes, setting the study area boundary and
       choosing the coordinate system to use.
    Automating the data involves digitizing or converting data from other systems and formats
       into usable formats as well as verifying the data and correcting errors.
    Managing the database involves verifying the coordinate systems and joining adjacent
       layers. The completeness and accuracy of the data used in the analysis determines the
       accuracy of the results.
Data inventory, input, manipulation and management

STEP THREE
Analyzing the data
Analysis and accuracy assessment. Analyzing GIS data ranges from simple mapping to complex
spatial models. Analysis methodology and list the major steps in the process. Create a systematic
diagram of the process as a guide.

Definition of a model: a model is a representation of reality, used to simulate a process, predict an
outcome or analyze a problem. A spatial model involves applying one or more of three categories of
GIS functions to some spatial data:
    Geometric modeling functions: calculating distances, generating buffers and calculating
       areas and perimeters.
    Coincidence modeling functions: overlaying datasets to find places where values coincide
    Adjacency modeling functions: allocating, pathfinding and redistricting.

STEP FOUR
Presentation of the results
    Poster-sized map
    Charts and reports of selected data are two ways of presenting the results
    Journal paper
    Powerpoint presentation


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