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So What is GIS???
“A collection of computer hardware, software and procedures that are used to organize, manage, analyze and display geographically referenced datasets.…"
Organizing Spatial Data
A GIS works with thematic layers of spatial data
Answer questions by comparing different layers of data
Five Components GIS
An integration of five basic components
A
Procedures
Query
Analyze
Store Display
Capture
Output
GIS Functions
Capturing Data
480585.5, 3769234483194.1, 3768432485285.8, 3768391484327.3, 3768565483874.7, 3769823
Coordinates
Paper maps Digital data
GPS
GIS Data
Components of Geographic Data
• Three general components to geographic information
AttributesGeometry
Streets
Behavior
Rules
Streets and highways may not intersect
Basic Elements of Spatial Data• Space
– Location in space requires a georeferncing system
• Time– Location in time
• Accuracy• Data Models and Formats• Attributes
– System for defining attributes
So How Do We Build A GIS?
X,Y X,Y X,Y
X,Y
Reality(A highway)
X,Y
Rows
Columns
Data Models• Vector formats
– Discrete representations of reality
• Raster formats– Use square cells to model reality
Vector Data
• Points, Lines and Polygons• Good for representing discrete objects: buildings roads, etc.• Smaller data storage needs
Raster Models• Good for modeling continuous data• Creation of surfaces• Modeling interactions between layers• Large data storage needs
Images & Grids
• Rows and columns of equal-sized cells – Each cell stores a value– Detail depends on cell size
• Grids (the ESRI native raster format)
• Images (TIFF, BMP, SID, JPEG, ERDAS)
Spatial Data Formats
ArcGIS works with multiple spatial data formats
ArcGIS
CAD
Coverage
GeodatabaseShapefile
Raster Tables
Internet Map Service
Which parcels are within 50 feet of the road?
Well type Drilled
Building owner Smith
Soil type Sandy
GIS Analysis Functions
• Proximity
• Overlay
• Network
MapsGraphs
Display
Reports
DocumentImage
Types of Output
InternetPaper map
GIS Data
