Maps from the Sky
Have you ever tried to make a map that contains six different kinds of information? One way is to use tracing paper or transparent sheets to provide one layer per set of information. Now biologists make complicated maps using a computer system called the "Geographic Information System" (GIS).

You may have seen one type of GIS tool -- a Landsat satellite photograph that shows different types of vegetation in different colors. Biologists are now working on "ground-truthing" the maps by comparing what the map shows with the plant communities they find on the ground.

If a Landsat photograph is accurate, it can become one layer of a multi-layered map. For example, in Montana biologists have been studying how elk use a logged area for food and shelter. One part of the map includes information from a ground-truthed Landsat map about the plant types in the study area. They'll add other information such as the locations of radio-collared elk at certain times of year and the locations of roads and streams. They'll also use satellites to track where hunters go.

To help with this study, hunters are carrying hand-held computers called Global Positioning System (GPS) units. The tiny computer calculates the hunter's exact route by using signals it receives from several satellites. Later, biologists download that information to a master program that adds the information to the same map containing the plant and elk information. To produce a finished map, the biologists select "print" from the computer menu -- no more transparencies or tracing paper.