Geographic information systems (GIS) are information systems or databases that are tied to maps. Think of GIS as a database with a map interface or a map with a database. You can access or interact with the data through the map (or vice versa), which makes GIS a fantastic query and analytical tool.

The figure below shows an example of a database and its related map. Each row in the database table is a unique spatial feature (e.g. a road segment or a stand of trees). Each table column is a different attribute or characteristic of the given feature (e.g. the road length or the type of trees).

GIS permit us to study data for geographic or spatial relationships or patterns. They are useful when one wishes to study simple spatial questions, spatial phenomena, or conduct more complex spatial analyses or modeling. An example of a simple query or classification would be to view population or density for a given region, as in the 2000 census for Northern Maine seen below. Here the absolute number of people is mapped per census block.

A more advanced set of queries could be used in a site location analysis. Let’s say we wish to locate a landfill, for example. Using distance from population centers, existing road access, location of environmentally sensitive habitat such as wetlands or eagle nesting sites, and other important criteria, GIS can be use to identify and buffer out undesirable characteristics to arrived at an optimum location. The example below is an analysis of distance from waterbodies for Washington County, Maine. Each criterion would be independently analyzed then merged to find a final desirable location.

Another interesting and useful aspect of GIS is its ability to use digital imagery as a data source. There are many forms of imagery, from scanned photographs to satellite imagery. The following is an example of digital aerial photography of the Fort Kent area taken in October of 2003.

Can you make out the railroad bridge in the center of the image? The UMFK campus is located on the south side of the oxbow bend in the Fish River.

There are many sources of data that can be used in GIS. They all have one important criterion. They must be in a digital format to be used.

Learn more about data sources in Geo280 GIS Applications I or For242 Map and Airphoto Interpretation. Both courses are offered annually in the spring. Another option, especially geared to Criminal Justice and Public Safety students, is the PSA122 course, GIS and GPS for Public Safety, offered each spring semester.