That gives you the option of viewing and analyzing each data item separately or in whatever combinations you need. Most GISes will import data and maps, and link them, with hints from you. Other systems process data and maps separately and can provide the linked information in a GIS-independent format. Ramas, from Applied Biomathematics of Setauket, N.Y., links maps with data for keeping track of endangered species. Claritas Select from Claritas Inc. of Arlington, Va., links maps with census data.
Government agencies produce a dizzying array of linked maps and data for many purposes.
Some of the simpler uses are voter registration maps or population maps. A step up might link a town's deed and title tasks with street, water, tax and zoning departments. The Army Reserve links maps with the locations of reservists for planning purposes. The National Imagery and Mapping Agency has a Digital Nautical Chart that links navigation charts with dynamic data on tide levels, water depth and currents. The Immigration and Naturalization Service links camera and Global Positioning System data to provide border surveillance.