A UTM grid reader is a transparent plastic scale that breaks down the 1000-meter grid into 10 or 100-meter divisions. This allows you to accurately measure the coordinates of a position on your map. You can buy special grid readers that also have lat/long scales, or you can buy a compass with a UTM grid reader on its base plate.

A good source for grid readers and lat/long scales is

Map World, 123-D North El Camino Real, Encinitas, CA 92024, (760) 942-9642, (800) 246-6277, maps@mapworld.com, http://www.mapworld.com