19 july 2000 iai summer institute gis: definition,...

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, andused to make decisions about, some portion ofthe Earth.

GIS - Geographic InformationSystems

Some GIS Examples

Some GIS Examples

Some GIS Examples

Definitions Continued

¥ Star and Estes 1990: An information systemthat is designed to work with datareferenced by spatial or geographiccoordinates; both a database system withspecific capabilities for spatially-referenceddata, as well as a set of operations forworking with the data. A higher-order map.

Definitions Continued

¥ Clarke (1997), referring to Burrough(1986): A powerful set of tools for storingand retrieving at will, transforming anddisplaying spatial data from the real worldfor a particular set of purposes.

¥ Clarke (1997) again: Automated systems forthe capture, storage, retrieval, analysis anddisplay of spatial data.

Definitions Continued

¥ Ron Abler (1988): GIS are simultaneouslythe telescope, the microscope, the computer,and the Xerox machine of regional analysisand 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)

Æ

Æ

(X1,Y1)

(X2,Y2)

(X3,Y3)

(X4,Y4)(X5,Y5)

(X6,Y6)

(X7,Y7)(X8,Y8)

(X9,Y9)

(X10,Y10)(X1,Y1)

(X2,Y2)

Spatial Elements in aVector World

¥ Point¥ Line¥ Area (Polygon)¥ Surfaces

Source: DeMers 1997

Vector Data Structure

Source: http://www.utexas.edu/depts/grg/gcraft/notes/datacon/datacon.html#Vector

Vector Data ModelPoints

Lines

Areas or Polygons

Model - Simplified representationof the patterns or processes of asystem. In this case, the Earth sSurface (not Clarke s definition).

Vector Data Model

Raster Data Model

Raster Data Model

9

11

7 3

11

11 11

9 9 9

3

3

3

3

3

3333

3

3

3

3 7

7

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

Source: DeMers

Also:MinimumMappingUnit (MMU)

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 HasReal X,Y Coordinates

—Resolution Depends onCell Size

—Each Cell has SingleAttribute (may link toseparate attribute table)

¥ VECTOR—Points, Lines, Polygons

with TopologicalRelationships andReal X,YCoordinates for AllFeatures

—Resolution Depends onSource Data

—Objects may have aNumber of Attributes

—Each Feature hasUnique IdentifierLinking it toDescriptive Attributes

Organizing Data andInformation

¥ Information can be organized as lists,numbers, tables, text, pictures, maps, orindexes.

¥ Clusters of information called data can bestored together as a database.

¥ A database is stored in a computer as files.

SHOESBaltimore Orioles39o20 N 76o38 WNew York Yankees40o40 N 73o58 W

Figure 2.1 The Elements of a GIS. (1) The Database (shoebox); (2) The Records (Baseball Cards); (3) TheAttributes (The categories on the cards, such as a batting average; (4) The geographic information (loca-tions 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 columnheaders and records as rows.

¥ The content of an attribute for one record isa value.

¥ A value can be numerical or text.

Flat File Database

Record Value Value Value

Attribute Attribute Attribute

Record Value Value Value

Record Value Value Value

The GIS Database (ctd)

¥ Data in a GIS must contain a geographicreference to a map, such as latitude andlongitude.

¥ The GIS cross-references the attribute datawith the map data, allowing searches basedon 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 ofEntities and Attributes

¥ A jump from databases to geographicrepresentation - 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: CaseStudy

¥ Camp Pendleton Case Study

¥ Go tohttp://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

ArcView¥ Run ArcView

—Add Extensions

¥ File Structure—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 1018 7 significant digits)

¥ CONVERT

127 156 144 5

127 5 5 127127 5 127 127

5 5 127 127

115 134 117 115

127156144

134117114

Actuallystored as:

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