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What is GIS?
A Geographic Information System (GIS) is a computer system that provides tools to store, edit, display and query data containing locational information, such as address, folio, census tract, Zip Code or x,y coordinates. The GIS allows you to view your data in a totally different way than has traditionally been done with spreadsheets and database table lists. Trends, patterns and relationships between features that have not been analyzed together in the past are easily seen in a GIS.

Although a GIS can create attractive maps, it is not a "map-maker" software. The map is typically the result of the analysis performed on your data or questions you have posed...

	Display all properties that are within 1000ft of a given address?
	Which is the best site for a new school?
	Where are hazardous materials stored relative to a reported fire incident?
	Show me the hot spots for car thefts?
	Where is the closest park with a pool?

To satisfy these types of questions, the appropriate data must be loaded into the GIS. The process of converting paper maps and other locational data into digital maps is often the most costly part of implementing a GIS. Data are entered as layers by common theme; for example, crime incidents are stored in one layer as points, properties are stored as polygons (areas) and street centerlines are stored as a layer of lines. Each individual feature is stored with its locational information (geographic coordinates) and its descriptive information. To view all the layers stored in the GIS together, they must all be in the same coordinate system.

GIS Layers diagram

Geographic Information Systems combine many disciplines and technologies, such as cartography, computer science, surveying, engineering and geodesy. Many of the complementary technologies that are used include Computer-Aided Design (CAD), Global Positioning Systems (GPS) and Image Processing Packages.

Why Use a GIS?

	Local government environments are well-suited for GIS because 90% of their data is related to geography; specifically address and tax folio.
	A GIS provides an efficient method for the maintenance and storage of maps.
	Analysis of data from multiple departments (and seemingly un-related) is possible based simply on the geography.
	Patterns, trends and relationships are identified and spatially analyzed

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This page was last edited on: March 17, 2003