(1) A map showing the general location and coverage of other maps, aerial photographs or points of interest. (2) A map showing the location, sheet lines and reference codes of maps in a map series.
Reference map sheet which outlines a mapping area and identifies all map sheets or sub-map sheets required to see the entire mapping area in detail.
A map which is used as a reference in the location of the more detailed, large scale maps needed for a particular project. Typically index maps do not contain detail beyond that necessary to locate the map required, by name, location or other relevant identifying information.