MGRS
The Military Grid Reference System (MGRS) is a grid-based system used to represent locations on the universal transverse Mercator (UTM) and universal polar stereographic (UPS) grid systems, expressed as an alphanumeric string. An MGRS coordinate defines an area on the Earth's surface as opposed to a specific point. A fully qualified MGRS string is 15 characters long and consists of the following three components: grid zone designation, 100,000-meter square identifier, and easting/northing.
Caution:Be aware that the location defined by an MGRS coordinate string is an area, not a specific point; however, the MGRS coordinate is displayed as the lower left corner of the area that it represents.
Grid zone designation
The first component, referred to as the grid zone designation (GZD), is composed of the first three characters of the MGRS string. The first two characters of the GZD represent the vertical UTM zone that the location falls in, while the third character represents the latitude band that the location falls in. UTM zones are generally 6 degrees wide and are numbered 01 through 60, starting at 180 degrees west longitude heading eastward. There are 20 latitude bands, identified C through X (excluding I and O so as not to be confused with the numbers 1 and 0) and are generally 8 degrees high starting at 80 degrees south heading northward. For more information about MGRS, including UTM zone and latitude band exceptions, see the publication DMA Technical Manual 8358.1: Datums, Ellipsoids, Grids and Grid Reference Systems.
Note:For areas north of 84 degrees north and south of 80 degrees south, the grid zone designation does not contain a UTM grid zone number. It does, however, contain the latitude band identifier. Valid latitude band identifiers for the polar regions are A and B for the southern pole and Y and Z for the northern pole.
100,000-meter square identifier
The second component of an MGRS string, the fourth and fifth characters, is the alpha character identifier of the 100,000-meter square within the GZD that the location falls in. The first character identifies the square in the longitudinal direction; the second identifies the square in the latitudinal direction.
Note:It is common practice under certain situations not to specify the first two components of the MGRS coordinate string. For example, if all users who are exchanging MGRS coordinates are working within the same grid zone designation or 100,000-meter square, it is not necessary to specify these components, because all participating users know they are all working within the same area. For information on how to specify where ArcGIS should obtain these values when the user does not specify them, see Modifying the MGRS locator settings.
Easting and northing
The third component represents the numeric easting and northing values within the 100,000-meter square and are measured from the lower left corner of the square.
Caution:Always express the easting and northing values using the same number of digits; for example, if you specify the easting using three digits, the northing must be specified using three digits.
MGRS precision
An MGRS coordinate represents an area on the Earth's surface as opposed to a specific point. The precision of the area defined by the MGRS coordinate is dependent on which components are expressed in the coordinate string; each successive component defines an area to a higher precision.
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11SMT |
Defines location down to 100,000-meter square |
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11SMT11 |
Defines location down to 10,000-meter square |
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11SMT1212 |
Defines location down to 1,000-meter square |
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11SMT123123 |
Defines location down to 100-meter square |
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11SMT12341234 |
Defines location down to 10-meter square |
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11SMT1234512345 |
Defines location down to 1-meter square |