What is GIS?

What is Geographic Information Systems (GIS)?

Geographic Information Systems are computer based tools for mapping and analyzing features and events on earth. GIS technology integrates common database operations such as query and statistical analysis with the unique visualization and geographic analysis benefits offered by maps.

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GIS maps, like the one above, are made up of collections of similar geographic objects (features) arranged in layers. It is this layering that gives GIS its unique display and analysis properties.

The map is created using a base County Map with towns and villages. Additional layers are added to create the completed map.

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Anything on earth can be represented in a GIS as a feature:

Picture of golf course.Course map BEFORE features

Picture of golf course.Course map with POLYGONS

Picture of golf course.Course map with POINTS

Picture of golf course.Course map with LINES

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Map showing GIS information.

Every feature in a GIS map has a record in a table linked to it. For example, a sewer pipe (represented by a line) can have information about its length, diameter, flow rate, most recent maintenance, or an endless list limited only by the user’s needs. These are known as a feature’s attributes. In the map you can highlight (select) a feature, open up the table, and examine all the information related to it. Or you can select a record in the table to see where the feature is on the map.

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The tables behind the features enable a GIS user to find information about them and display the results on a map by performing queries. Like which towns are over 30 square miles in size?

Picture of map showing query results.

Or which towns have over 10,000 households?

Picture of map showing query results.

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Spatial Queries

Picture of map showing spatial queries.

A GIS user can also query features based on their location in relation to other ones-what is near what, how many are in that one, how close is this to that, and so on. For example, which towns have golf courses within their borders?

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Thematic Maps

Features can be classified by the data in the attribute tables and displayed in thematic maps. For example, a dot density map of population:

Picture of a thematic map.

Or in a map showing the same results a different way, the darker the color the higher the density:

Picture of a map showing other results.

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Extending GIS

Picture showing extended capabilities of GIS.

GIS isn’t limited to flat maps and databases. There are many extensions to the basic software packages that enable things such as three dimensional visualization and analysis and much more.

Picture of three dimesion visualization of map.

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