(Data West Research Agency definition: see GIS glossary.) A map definition level of a virtual map. It describes the street, water, sewer, gas, electric, phone and cable networks together with the cumulated structures developed to meet the needs of the people within the land area. The facility area data files describe and define the street network and street facilities of the area with locational coordinates associated with the facilities and supplemental identifiers. The facility definition (street network), when related to spatial display, uses a base geography area definition.

A GIS provides a framework for data manipulation and display of map data especially for (a) location verification, (b) location correlation, (c) locational relationships, (d) district coding, (e) route analysis, (f) area analysis and (g) mapping/display creation.