What is used to convert an azimuth from grid to magnetic on a map?

The declination diagram is a key feature found on most military maps, providing a visual representation of the relationship between grid and magnetic north. It specifically illustrates the angle of difference, or declination, between the grid lines on the map and true magnetic north in the field. When converting an azimuth from grid to magnetic, one must refer to this diagram to determine the appropriate adjustment, either adding or subtracting the declination value based on the map's orientation and the direction of travel.

Using a compass alone does not directly facilitate the conversion of azimuths from grid to magnetic, as it may not provide the specific angle needed for that particular map. The map legend primarily conveys information about map symbols and scales rather than assisting with navigation adjustments. The topographic scale offers information about distances and elevations on the map but does not provide the necessary data for converting azimuths.