(Data West Research Agency definition: see GIS glossary.) A category level of a virtual map. It describes the constraints and controlling interest which exist over the land area. It describes parcel deed descriptions, subdivision plans, ordinances controlling zoning, rights-of-way and easements, and related judicial interests in the land area, which altogether comprise the legal area definitions of the area map. Legal area definitions are overlays to the base geography and, indeed, could not exist without serious conflict if precise locational methodology were not used. The classic problem is the municipal boundary description which references the "old oak tree" which happened to have died fifty years ago and today no one can determine where it grew.