The Military Grid Reference System (MGRS) is the coordinate system that NATO forces use worldwide to designate a position unambiguously. Where ordinary GPS coordinates describe a spot with latitude and longitude, MGRS divides the earth into a grid of rectangular squares. That makes a position shorter to write down, easier to pass along over the radio and less prone to reading errors.
What does an MGRS coordinate consist of?
A full MGRS reference consists of three parts, from coarse to fine:
- Grid Zone Designator (GZD) — a number from 1 to 60 followed by a letter, for example
31U. The number is the UTM zone (each 6° wide), the letter is the latitude band. - 100,000-meter square — two letters, for example
ET, that identify a 100 × 100 km square within the zone. - Numeric location — an even number of digits that gives the easting (to the right) and northing (upward) within that square, for example
12345 67890.
Together that yields a reference like 31U ET 12345 67890. The more digits, the more precise the position.
Why MGRS instead of GPS degrees?
Decimal degrees such as 52.3676° N, 4.9041° E are hard for people to remember and error-prone to communicate. An MGRS code is more compact, the grid is rectangular (which makes estimating distances easier) and there is no confusion about north/south or east/west. That is exactly why it is the standard in military and many search-and-rescue operations.
MGRS, UTM and WGS84
MGRS is not a separate system but a convenient notation on top of UTM (Universal Transverse Mercator). The underlying projection is the same; MGRS only replaces the coarse part of the UTM coordinate with letter combinations. The underlying positions are usually calculated on the WGS84 ellipsoid, the same reference frame that GPS uses.
Using MGRS in MilMap
MilMap supports MGRS throughout the application: you search by an MGRS coordinate, enter waypoints in MGRS format and every PDF export automatically shows the MGRS coordinate for each point. You set which format is shown per map, and MilMap converts between MGRS and other formats in the background.
Start with MilMap for free and work with MGRS coordinates right away.