Geographical Base

or geographic base of a map, elements of a thematic map that are not part of its special content. The geographic base facilitates orientation and the elucidation of laws governing the distribution of the phenomena relating to the map’s theme. The theme and purpose of a map determine the content and character of the geographic base. On small-scale thematic maps of the world and of continents the geographic base is frequently restricted to the depiction of the coastline, major rivers and lakes, and large cities. On maps with larger scales the geographic base may also indicate such phenomena as vegetation, relief, lines of communication, political and administrative boundaries, glaciers, and swamps. The geographic base is particularly detailed and graphic on maps designed for practical use, where it ensures the spatial localization of depicted phenomena.

In the compilation of thematic maps the geographic base serves as a kind of framework for cartographic representation and the plotting of specific content. In the compilation of serial thematic maps and atlases a standard geographic base is often prepared, which is then used for a number of interrelated maps.