(1) A map on which information can be placed for comparison or for geographical correlation. The term base map was at one time applied to a class of maps now known as outline maps. It may be applied to topographic maps (also called mother maps in jargon) which are used in the construction of many special types of maps by adding particular data. (2) A map from which other maps are prepared by adding information. In particular, a planimetric map used in preparing topographic maps.