The United States Military Grid Reference System (MGRS) is designed for use with UTM (Universal Transverse Mercator) and UPS (Universal Polar Stereographic) grid coordinate systems. The MGRS is an alphanumeric version of a numerical UTM grid coordinate.
The world is generally divided into 6° by 8° geographic areas, each of which is given a unique identification, called the Grid Zone Designation. These areas are covered by a pattern of 100,000‑meter squares. Each square is identified by two letters called tie 100,000‑meter square identification. A reference keyed to a gridded map of any scale is made by giving the 100,000‑meter square identification together with the numerical location.
The grid zones are divided into a pattern of 100,000‑meter grid squares forming a matrix of rows and columns. Each row and each column is sequentially lettered such that two letters provide a unique identification within approximately 9° for each 100,000‑meter grid square.
For that portion of the world where the UTM grid is specified (80° South to 84° North), the UTM grid zone number is the first element of a Military Grid reference. There are additional designations that express additional refinements.
MGRS Grid Zones
An example of an MGRS designation is:
The components of the MGRS values are:
Grid Zone Designation
- First two characters represent the 6° wide UTM zone.
- The third character is a letter designating a band of latitude. The 20 bands begin at 80° South and proceed northward. The letters are C through X, omitting I and O.
100,000-Meter Grid Squares
- The fourth and fifth characters designate one of the 100,000-meter grid squares within the grid zone.
Easting and Northing Values
The remaining characters represent the easting and northing values within the 100,000-meter grid square. The number of characters determines the amount of precision.
- 1 character = 10 km precision
- 2 characters = 1 km precision
- 3 characters = 100 meters precision
- 4 characters = 10 meters precision
- 5 characters = 1 meter precision
For a complete description, see the National Geospatial Intelligence Agency website http://earth