Intro to GIS

							Intro to GIS
October 24, 2006
           Announcements
 Second  Midterm Quiz is next week (covers
  chapters 6, 9, 10, 12 plus lectures
 Oslo Project description
 GIS Club Activity: Presentation by
  Thorbjørn Geirbo, today at 14.15 in the
  GIS Lab (HHH 035)
 GIS Day: Wednesday, November 15th.
               Oslo Project
            Examples from 2004
   Tilgjengelighet til legesentre i Bydel Grorud
   Innvandrernes bosettingsmønster
   Distinksjoner i Oslo: En Bourdieusk alanyse av
    ulikehet ved hjelp av geografiske
    informasonssystemer
   Sosiale skiller i Oslo
   Sosiale ulikheter i Oslo
   Inntekt og boligstruktur i Oslo: med fokus på
    bydel Gamle Oslo
   Privatisering og innntektsnivå i bydel Vestre
    Aker
         Examples from 2005
 Barnehagedekning i bydel St. Hanshaugen
 En treffsted for alle unge? Tilgjengelighet til
  fritidsklubber i Nordstrand og Østensjø bydeler
 Romlig analyse av sosiale forskjeller;
  segregering på Grünerløkka?
 Vestre Aker – mer enn bløtkakevillaer og
  Jaguarer (en casebasert diskusjon av GIS som
  geografisk analyseverktøy)
        Last Week’s Lecture
 Database   – an integrated set of data on a
  particular subject
 Databases offer many advantages over
  files
 Relational databases dominate
         A DBMS contains:
 Data definition language
 Data dictionary
 Data-entry module
 Data update module
 Report generator
 Query language
        Advantages of Databases
 Avoids redundancy and duplication
 Reduces data maintenance costs
 Applications are separated from the data
       Applications persist over time
       Support multiple concurrent applications
 Better data sharing
 Security and standards can be defined and
  enforced
                           SQL
 Structured (Standard) Query Language –
  (pronounced SEQUEL)
 Developed by IBM in 1970s
 Now de facto and de jure standard for accessing
  relational databases
 Three types of usage
       Stand alone queries
       High level programming
       Embedded in other applications
        Types of SQL Statements
   Data Definition Language (DDL)
       Create, alter and delete data
       CREATE TABLE, CREATE INDEX
   Data Manipulation Language (DML)
       Retrieve and manipulate data
       SELECT, UPDATE, DELETE, INSERT
   Data Control Languages (DCL)
       Control security of data
       GRANT, CREATE USER, DROP USER
             Spatial Relations
   Equals – same geometries
   Disjoint – geometries share common point
   Intersects – geometries intersect
   Touches – geometries intersect at common
    boundary
   Crosses – geometries overlap
   Within– geometry within
   Contains – geometry completely contains
   Overlaps – geometries of same dimension overlap
   Relate – intersection between interior, boundary or
    exterior
             Spatial Methods

   Distance – shortest distance
   Buffer – geometric buffer
   ConvexHull – smallest convex polygon geometry
   Intersection – points common to two geometries
   Union – all points in geometries
   Difference – points different between two
    geometries
   SymDifference – points in either, but not both of
    input geometries
              Spatial Search
 Buffering  is a spatial retrieval around
  points, lines, or areas based on distance.
 Overlay is a spatial retrieval operation that
  is equivalent to an attribute join.
Identify
Recode
    OR
 Data
overlay
Overlay
  Types of overlay operations
 And
 Or
 Max
 Min
Buffer (raster)
            +1
Buffer (vector)
     Complex Retrieval: Map
           Algebra
 Combinations of spatial and attribute
 queries can build some complex and
 powerful GIS operations, such as
 weighting.
                Review
A  geographic database contains both
 spatial and tabular data. The spatial data
 contains feature shape and location
 information, while the tabular data
 contains the attributes for the features.
 Often, feature attributes are contained in
 multiple tables.
Making Maps With
      GIS
                 Introduction
       is the pinnacle of GIS projects
 Output
 Two main types of output
     Maps
     Visualizations (see chapter 13)
     are good at summarizing and
 Maps
 communicating
          What is a map?
 “A graphic depiction of all or part of a
 geographic realm in which the real-world
 features have been replaced by symbols
 in their correct spatial location at a
 reduced scale.”




                                      power line
        Map function in GIS
 Storage
 Temporary    communication
 Intermediate check of data
 Final report
GIS Processing
Transformations
         Characteristics of Map
 Two   main types
     Topographic
     Thematic
 Some    map problems
     Can miscommunicate
     Each map is just one of all possible maps
     Complex maps can be difficult to understand
Topographic Map
Thematic Map
                Map Types
 Point data
 Line data
 Area data
 Volume data
 Time data
      Choosing a Map Type
 Cartographers   have designed hundreds of
  map types: methods of cartographic
  representation.
 Not all GISs allow all types.
 Most have a set of basic types
 Depends heavily on the dimension of the
  data to be shown in the map figure.
    Choosing the Wrong Type
 Fairly common GIS error.
 Due to lack of knowledge about
  cartographic options.
 Can still have perfect symbolization.
 Possibility of misinformation
 Definite reduction in communication
  effectiveness.
Choropleth
  Class
Schemes
              Choosing Types
 Check the data
    Continuous

    Discrete

    Accuracy & Precision

    Reliability

 Dimension (Point, Line, Area, Volume)
 Scale of Measurement (Nominal, ordinal, etc.)
 GIS capability
 Is there a need to supplement GIS software? (e.g. with a
  drawing package)
        Maps and Cartography
 Map  – ‘digital or analog output from a GIS
  showing information using well established
  cartographic conventions’
 Cartography is the art, science and
  techniques of making maps
        The Need for Design

 To appear professional and avoid errors,
  GIS maps should reflect cartographic
  knowledge about map design.
 A map has a visual grammar or structure
  that must be understood and used if the best
  map design is desired.
 Cartographic conventions should be
  followed (e.g. forests should be green).
             Map Design
 Good  map design requires that map
  elements be placed in a balanced
  arrangement within the neat line.
 A GIS map is designed in a process called
  the design loop.
 Primary goals in map design: to share
  information, highlight patterns and
  processes, and illustrate results.
To be effective, a map must
 be correctly designed and
        constructed.
The Parts of a Map: Map Elements
 Neat line                  Border                             Title

                      The United States of America

Figure


                                                                       Legend

    Ground                                                   Washington,D.C.
                                                                                     Scale
                                                             National Capital
             Alaska                                             0 1 2 3 4
                       Hawaii                                    hundreds of
                                                                 kilometers


                                            Lambert Conformal Conic Projection
                      0 4       04                   Source: U.S. Dept. of State




    Inset              Place name      North Arrow                              Credits
                                                 Inset map




                          Scale
                                                      Author




                                  North Arrow



        Map Body                                Data Source




                                                  Projection
                                     Legend
Title              Grid
Bertin's Graphic
  Primitives
       Visual balance is key!
 Visual balance is affected by:
 the "weight" of the symbols
 the visual hierarchy of the symbols and
  elements
 the location of the elements with respect to
  each other and the visual center of the
  map.
       Visual center


                      5% of height

       5% of height




Landscape                Portrait
         Visual Layout
Title Here




                               Title Here




  Eye expects (1) balance and (2) alignment
Text: Selection and Placement


Kristiansand




                                                  Bærum
                                                          Oslo
 BM 232

POINT                              LINE                                    AREA
  Some cartographic label placement conventions. Points: right and above preferred with no overlap.
  Lines: Following the direction of the line, curved if a river.
  Areas: On a gently curved line following the shape of the figure and upright.
            Text placement
Trondheim
                     Trondheim
                                 Path right
   Trondheim
                                      P
                    Trondheim
                                      a
                                      t
                                      h
                                      D
   Bogstadvann                        o
                                      w
                                      n
              Symbol “weight”

Line weight     Pattern   Shading   Hue
         Map Design and GIS
 When   a GIS map is the result of a
  complex analytical or modeling process,
  good design is essential for
  understanding.
 The map is what distinguishes GIS as a
  different approach to the management of
  information, so extra care should be taken
  to improve the final maps that a GIS
  generates in a GIS task.
    Limitations of Paper Maps
 Fixed  scale
 Fixed extent
 Static view
 Flat and hence limited for 3D visualization
 Only presents ‘complete’ world view
 Map producer-centric
              Conclusions
 Cartography  is both an art and a science
 Maps are fundamental to GIS projects
 Modern advances in cartography make it
  easy to produce good and bad maps
 New technology and especially the
  Internet has change the content and
  techniques of GIS-based cartography
Multivariate Mapping
Part II: Working with
Attributes in ArcGIS
           Issues to discuss
 how   attribute data is stored in a table of
  rows and columns
 how attribute data is associated with
  features
 tabular field types supported in ArcGIS
 types of table relationships
 how tables can be related to each other
 how to join tables based on a common
  field
         Anatomy of a Table
 Each table in a database has the same basic
  format: an array of rows and columns. Rows are
  also called records, and columns are also called
  fields.
 Some tables, like a feature class's default
  feature attribute table, have a preset number of
  columns. For instance, a polygon coverage's
  feature attribute table has four standard
  columns: Area, Perimeter, Coverage#, and
  Coverage-ID, while a line shapefile's feature
  attribute table has only one default column,
  named Shape. Other tables are completely user-
  defined.
   The table has three user-added columns: Name,
    Country, and Population. ArcMap automatically adds a
    third column (FID) for display purposes. The name of this
    column may be different depending on the type of data
    source. For example, it is called FID for a coverage or
    shapefile, OBJECTID for a geodatabase feature class,
    and Order_ID for a grid.
   Because some databases and some operations do not
    support fields with blanks in their names, you should
    avoid creating fields that contain them. In addition, every
    column in a table should have a unique name but
    columns in the same table can have a variety of formats.
    NOTE: Norwegian “æ å ø” can also create problems, as
    can decimal formats (10,1 versus 10.1).
       Tabular data field types
 Tables are capable of storing date, number, and
  text values, but most tabular formats have
  several different field types to store this
  information.
 Choosing the best field type for the values to be
  stored is an important consideration. Also, the
  available field types can vary between tabular
  formats. In general, you can store numbers, text,
  and dates. Specifically supported formats in
  ArcCatalog include short integer, long integer,
  float, double, text, date, object-id, and blob.
Information stored in tables is organized by fields and field types. When defining a
table's fields, be aware that each database has its own rules defining what names and
characters are permitted.
       ArcGIS Tabular Formats
 ArcGIS supports the use of multiple formats for storing
  and managing tabular data. Each of ArcGIS software's
  primary spatial formats has its own native format.
  Coverages use INFO-formatted tables; shapefiles store
  their attributes in dBASE (.dbf) format; geodatabases
  rely on the format of their supporting RDBMS (Oracle, for
  example).
 Deciding on the proper format in which to store attribute
  information is an important part of database design and
  can affect the efficiency with which you are able to
  access feature attributes. To facilitate sharing data that's
  in different formats, ArcCatalog and ArcToolbox contain
  tools to convert between the various tabular formats. In
  addition, some formats, such as the coverage, can link to
  independent tables regardless of their format.
Tabular information can be stored in a variety of formats. In this case, feature
information is stored in the coverage feature attribute table, data about the owners is
stored in dBASE format, and tax information is stored in a relational database
format.