In 1974, USGS designated the UTM grid system as the national standard for large scale maps such as 7.5 and 15 minute series topographic map sheets. Compared to latitude and longitude, it is significantly easier to use. GPS users will find this a real advantage. All new edition USGS topographic maps have the UTM grid printed on them.
This grid reader will work on eight different map scales. Instructions on the back of the packaging provide a basic explanation for using the reader.