Military Grid Reference System: Difference between revisions

Revision as of 21:03, 25 June 2025

Revision as of 21:37, 25 June 2025

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{{Short description|NATO global coordinate reference system}}

{{Geodesy}}

The '''Military Grid Reference System''' ('''MGRS''')<ref name="DMA8358_1_Chapter3">[http://earth-info.nga.mil/GandG/publications/tm8358.1/tr83581b.html#ZZ26 DMA Technical Manual 8358.1, Chapter 3.] Datums, Ellipsoids, Grids, and Grid Reference Systems</ref> is the geocoordinate standard used by [[NATO]] militaries for locating areas on Earth. The MGRS is derived from the [[Universal Transverse Mercator coordinate system|Universal Transverse Mercator (UTM)]] grid system and the [[Universal polar stereographic coordinate system|Universal Polar Stereographic (UPS)]] grid system, but uses a different labeling convention. The MGRS is used as [[geocode]] for the entire Earth. It’s also referred as 10-digit coordinates.

An example of an ''MGRS coordinate'', or ''grid reference'', would be [{{Coor URL}}21_18_34.0_N_157_55_0.7_W_&language=en 4QFJ12345678], which consists of three parts:

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* 1234 5678 (numerical ___location; [[Easting and northing|easting]] is 1234 and [[Easting and northing|northing]] is 5678, in this case specifying a ___location with 10&nbsp;m resolution)

An MGRS grid reference is an alphanumeric value that represents a square area on the Earth's surface, rather than a single point.<ref>{{cite web |url=https://pro.arcgis.com/en/pro-app/latest/help/mapping/properties/military-grid-reference-system.htm |title=Military Grid Reference System |website=ArcGIS Pro |publisher=Esri |access-date=25 June 2025 |quote=An MGRS coordinate defines an area on the Earth's surface as opposed to a specific point.}}</ref> When the termA ''grid square'' isreferences used,a itsquare canon referthe to a squareEarth with a side length of 10&nbsp;km, 1&nbsp;km, 100&nbsp;m, 10&nbsp;m or 1&nbsp;m, depending on the precision of the coordinates provided. (In some cases, squares adjacent to a Grid Zone Junction (GZJ) are clipped, so "polygon" is a better descriptor of these areas.)

The number of digits in the numerical ___location must be even: 0, 2, 4, 6, 8 or 10, depending on the desired precision. When changing precision levels, it is important to [[truncate]] rather than [[rounding|round]] the easting and northing values to ensure the more precise polygon will remain within the boundaries of the less precise polygon.

Related to this is the primacy of the southwest corner of the polygon being the labeling point for an entire polygon. In instances where the polygon is not a square and has been clipped by a grid zone junction, the polygon keeps the label of the southwest corner as if it had not been clipped.

* 4Q ......................GZD only, precision level 6° × 8° (in most cases)