Military Grid Reference System (MGRS)

The Military Grid Reference System (MGRS) is a two-dimensional grid that uniquely identifies a square meter anywhere on the earth. The MGRS attempts to represent the entire surface of the Earth on a worldwide grid. The grid is based on the UTM (between 80°S and 84°N latitudes) and UPS (Universal Polar Stereographic) systems.

Currently, GeoCalc only supports MGRS points in the UTM-based latitude range (between 80°S and 84°N ).

MGRS coordinates are comprised of 7 parts, 3 of which correspond to the UTM/UPS zone that contains the coordinate. In addition to the Datum (which is not explicitly expressed in the MGRS coordinate), the UTM/UPS zone and latitude band (described below) are part of the MGRS point.

UTM

• The UTM area is divided into 60 longitudinal strips, each 6° wide. The strips are numbered 1-60 beginning at the 180°-174° W (Zone 1) and increase to the East (i.e. 174°-168° W = Zone 2, etc.).

• Each strip (i.e. Zone) is then divided (horizontally) into 8° latitude bands. The bands are lettered “C” (80° S) through “X” (80° N) omitting the letters “I” and “O”.

MGRS Coordinates

The MGRS coordinate consists of seven parameters:

1. Datum (as applied to MGRS)

   Equivalent to corresponding UTM/UPS datum, and thus is not expressed explicitly in the coordinate.

2. Zone Number

   Equivalent to corresponding UTM/UPS zone number.

   Example:
   19TDJ3858897366
   “19” is equivalent to the corresponding UTM zone.

3. Band Letter
   

   Equivalent to UTM/UPS latitude band letter.

   Example:
   19TDJ3858897366
   “T” is the corresponding UTM latitude band letter.

4. MGRS Column Letter
   

   This is the first of 2 letters used to define the 100 kilometer square within the UTM/UPS block. The columns A-Z (excluding "I" and "O"), like UTM, start at 180° and increase toward the East. Every 3 columns, the pattern repeats.
   

   Example:
   19TDJ3858897366
   “D” is the MGRS column letter

5. MGRS Row Letters
   

   This is the second of 2 letters used to define the 100 kilometer square within the UTM/UPS block. Row letters increase to the North. The letters cycle backwards through the alphabet in the southern hemisphere (J, H, G, ... going south).Zone 1, A-H; Rows

6. MGRS Easting
   

   MGRS Easting value consists of 5 digits. Represents the number of meters east of the origin (i.e. southwest corner) of the 100 kilometer square in which it is contained.
   

   Example:
   19TDJ3858897366
   “38588” is the MGRS Easting value

7. MGRS Northing

   MGRS Northing value consists of 5-digits. Represents the number of meters north of the origin (i.e. southwest corner) of the 100 kilometer square in which it is contained.

   Example:
   19TDJ3858897366
   “97366” is the MGRS Easting value

References:

Parker, W. and Bartholomew, R., Issues in Automating the Military Grid Reference System, IN: The Fifth International Geodetic Symposium on Satellite Positioning, Vol. II, 903-913.

Parker, W.S., and Bartholomew, R.G., 1988, Mapping, Charting, and Geodesy in the DoD Standard GPS Receivers, IEEE Plans Record, 145-152.