GIS: Definition, Software IAI Summer Institute 19 July 2000
What is a GIS? Geographic Information System Definitions DeMers (1997): Tools that allow for the processing of spatial data into information, generally information tied explicitly to, and used to make decisions about, some portion of the Earth.
GIS - Geographic Information Systems
Some GIS Examples
Some GIS Examples
Some GIS Examples
Definitions Continued Star and Estes 1990: An information system that is designed to work with data referenced by spatial or geographic coordinates; both a database system with specific capabilities for spatially-referenced data, as well as a set of operations for working with the data. A higher-order map.
Definitions Continued Clarke (1997), referring to Burrough (1986): A powerful set of tools for storing and retrieving at will, transforming and displaying spatial data from the real world for a particular set of purposes. Clarke (1997) again: Automated systems for the capture, storage, retrieval, analysis and display of spatial data.
Definitions Continued Ron Abler (1988): GIS are simultaneously the telescope, the microscope, the computer, and the Xerox machine of regional analysis and synthesis of spatial data.
GIS According to ESRI
Kinds of GIS Data Representation Vector Point Line (Arc) Area (Polygon) Points, Lines, and Areas in Space Raster Grid Hexagons, others Quasi-Continuous Surface in Space
Vector Data Model Æ(X,Y) (X 1,Y 1 ) (X 10,Y 10 ) (X 1,Y 1 ) Æ (X 2,Y 2 ) (X 3,Y 3 ) (X 4,Y 4 ) (X 5,Y 5 ) (X 9,Y 9 ) (X 6,Y 6 ) (X 2,Y 2 ) Æ (X 7,Y 7 ) (X 8,Y 8 )
Point Line Area (Polygon) Surfaces Spatial Elements in a Vector World Source: DeMers 1997
Vector Data Structure Source: http://www.utexas.edu/depts/grg/gcraft/notes/datacon/datacon.html#vector
Points Vector Data Model Areas or Polygons Lines Model - Simplified representation of the patterns or processes of a system. In this case, the Earth s Surface (not Clarke s definition).
Vector Data Model
Raster Data Model
Raster Data Model 93 3 3 3 3 9 9 9 3 11 11 3 3 11 11 7 3 7 7 3 3 3 3 3 3
Raster Data Structure Source: http://www.utexas.edu/depts/grg/gcraft/notes/datacon/datacon.html#raster
Raster Data Structure
Raster Representation of Point, Line, Area Also: Minimum Mapping Unit (MMU) Source: DeMers
Raster Data Structure Source: Clarke, K.C. 1999. Getting Started with GIS. Prentice-Hall.
Vector Data Structure Any better?
Raster vs. Vector RASTER Simple Data Structure Rows/Columns of Equal-Size Grid Cells, Each of Which Has Real X,Y Coordinates Resolution Depends on Cell Size Each Cell has Single Attribute (may link to separate attribute table) VECTOR Points, Lines, Polygons with Topological Relationships and Real X,Y Coordinates for All Features Resolution Depends on Source Data Objects may have a Number of Attributes Each Feature has Unique Identifier Linking it to Descriptive Attributes
Organizing Data and Information Information can be organized as lists, numbers, tables, text, pictures, maps, or indexes. Clusters of information called data can be stored together as a database. A database is stored in a computer as files.
SHOES Baltimore Orioles 39 o 20 N 76 o 38 W New York Yankees 40 o 40 N 73 o 58 W Figure 2.1 The Elements of a GIS. (1) The Database (shoebox); (2) The Records (Baseball Cards); (3) The Attributes (The categories on the cards, such as a batting average; (4) The geographic information (locations of the team s stadium in latitude and longitude); (5) A means to use the information (the computer). Source: Clarke 1999
The GIS Database In a database, we store attributes as column headers and records as rows. The content of an attribute for one record is a value. A value can be numerical or text.
Flat File Database Attribute Attribute Attribute Record Value Value Value Record Value Value Value Record Value Value Value
The GIS Database (ctd) Data in a GIS must contain a geographic reference to a map, such as latitude and longitude. The GIS cross-references the attribute data with the map data, allowing searches based on either or both. The cross-reference is a link.
Relational Database Terms Entities = in GIS, points, lines, areas, surfaces (Vector), Grid Cell (Raster). Attributes = Information about the Entities Tuples = Ordered records of rows of attribute values.
Why Relational?
Geographical Representation of Entities and Attributes A jump from databases to geographic representation - difficulties? Several other attributes come into play: Location Connections Angles and distances Neighbors Topology
Sources of GIS Data See Pointer MWB Web Site http://www.clas.ufl.edu/users/mbinford/geo317 1/Pointers_to_WWW_GIS_Resources.html
What can we do with GIS: Case Study Camp Pendleton Case Study Go to http://www.gsd.harvard.edu/brc/brc.html
Camp Pendleton, CA Context Region
Region of Camp Pendleton
Land Cover 1990+
Plans Build-Out
Comparison 1990+ and Plans Build-Out Land Cover 1990+
Various Data
Various Analyses
Final Results - Conservation Priority
The Software: Idrisi Run Idrisi Environment File Structure Raster and Raster Documentation Files Run ArcView Add Extensions File Structure ArcView Feature, Image, and Grid Files
Idrisi http://www.idrisi.clarku.edu/
IDRISI System Basics WINDOWS SCREEN - run IDRISI Menu System Tool Bar Status Bar Program Modules Setting the Working Directory Working with IDRISI dialog boxes Pick Lists Automatic Output File Names Overwrite Protection HELP FILES!!!!!!
IDRISI System Basics MAP LAYERS (Displayed) Image Layers -.rst and.rdc files Vector Layers -.vct and.vdc files MAP LAYER FILE STRUCTURES Image Files Integer Files (+/- 32767 16-bit integers) Byte Files (0-255 8-bit integers) Real Number Files (+/- 1 x 10 18 7 significant digits) CONVERT 127 156 144 5 127 5 5 127 127 5 127 127 5 5 127 127 115 134 117 115 Actually stored as: 127 156 144 134 117 114
Idrisi System Basics Other File Types (not displayed) Attribute Values Files and Documentation Files Symbol and Palette Files Reference System Parameter Files Group Files Map Composition Files
Idrisi System Basics Displaying Maps and Map Layers Display launcher Map Window Composer Printer Workshop Symbol Workshop Palette Workshop
ArcView
ArcView Windows: Project, View, Table, Layout Selections: Map, Table Legend Editor Query, Measurement, Analyses