Geographic Information Geographic Information SystemSystem

By: By:

Scott WiegalScott Wiegal

Mitchell Mathews Mitchell Mathews

What is GIS?What is GIS?

GIS represents real world objects that are GIS represents real world objects that are spatially referenced (have a location).spatially referenced (have a location).

There are two types of reference points; There are two types of reference points; either absolute (e.g., latitude/longitude) or either absolute (e.g., latitude/longitude) or

relative (what’s it next to?)relative (what’s it next to?)

Space can be conceptualized into two Space can be conceptualized into two abstractions: Discrete (raster) and abstractions: Discrete (raster) and

Continuous (vector).Continuous (vector).

RasterRaster

Made up of individual cells Made up of individual cells each with their own valueeach with their own value

e.g., Color is defined by 8 bits e.g., Color is defined by 8 bits for Red, Green, and Blue; for Red, Green, and Blue; 24 bits24 bits

Once created; can’t be scaled to a larger size or to a Once created; can’t be scaled to a larger size or to a lower resolution without loss of qualitylower resolution without loss of quality

Raster graphics are more practical than vector Raster graphics are more practical than vector graphics for photographs and photo-realistic graphics for photographs and photo-realistic imagesimages

VectorVector

Made up of points, lines, Made up of points, lines, and polygonsand polygons

One defined color for the One defined color for the line and one for the fill-inline and one for the fill-in

Plotting of points doesn’t lose quality when Plotting of points doesn’t lose quality when resolution is changedresolution is changed

Vector graphics are more practical for Vector graphics are more practical for boundariesboundaries

Raster Vs VectorRaster Vs Vector

Raster Discrete

Vector Continuous

Raster Vs VectorRaster Vs Vector

Vector AdvantagesVector Advantages1. Minimal amount of 1. Minimal amount of

informationinformation

allows for smaller file size.allows for smaller file size.

2. Indefinite zoom will keep 2. Indefinite zoom will keep

lines clear and proportionallines clear and proportional

3. Use of arbitrarily precise 3. Use of arbitrarily precise (X,Y)(X,Y)

coordinates allows for morecoordinates allows for more

accurate measurementsaccurate measurements

Raster AdvantagesRaster Advantages1. Easier and more descriptive 1. Easier and more descriptive

use use

of combining layersof combining layers

2. Displays varying surface 2. Displays varying surface featuresfeatures

more effectivelymore effectively

3. Ideal for satellite imagery3. Ideal for satellite imagery

because of its detailed because of its detailed naturenature

Applications – ArcGIS (ESRI)Applications – ArcGIS (ESRI)

Vector program for GIS & Mapping Vector program for GIS & Mapping SoftwareSoftware

77% of GIS professionals use some 77% of GIS professionals use some formform

Desktop, Server, and Desktop, Server, and

Mobile offeringsMobile offerings

Applications – ArcIMS (ESRI)Applications – ArcIMS (ESRI)

Is an Internet Mapping SolutionIs an Internet Mapping Solution Ideal for sharing information online Ideal for sharing information online

due to its multi-tier systemdue to its multi-tier system

Applications – IDRISI (Clark Applications – IDRISI (Clark Univ.)Univ.)

Raster geographic software packageRaster geographic software package Inexpensive but professionalInexpensive but professionalMost widely used raster system in Most widely used raster system in

worldworld

Applications – GRASS (Open Applications – GRASS (Open Src)Src)

GRASS – Geographic Resources GRASS – Geographic Resources Analysis Support SystemAnalysis Support System

Package of 350 programs that deals Package of 350 programs that deals in both vector and rasterin both vector and raster

Uses - MapquestUses - Mapquest

Corvallis – City Level

Corvallis – Street Level

Uses – FirefightingUses – Firefighting

Vector

Raster

Uses – Wildlife MgmtUses – Wildlife Mgmt

Raster

Vector

Uses – Real EstateUses – Real Estate

Uses - InsuranceUses - Insurance

FinFin