Content deleted Content added
Changed first example to align with later examples on precision Tags: Mobile edit Mobile web edit Advanced mobile edit |
the quoted source supports the definite article Tags: Mobile edit Mobile web edit Advanced mobile edit |
||
(12 intermediate revisions by 4 users not shown) | |||
Line 1:
{{Short description|NATO global coordinate reference system}}
{{Geodesy}}
The '''Military Grid Reference System''' ('''MGRS''') is the geocoordinate standard used by [[NATO]] militaries for geo-referencing, position reporting, and situational awareness during land operations.<ref>{{cite
An example of an ''MGRS coordinate'', or ''grid reference'', is [{{Coor URL}}
* <code>4Q</code> (grid zone designator, GZD)
* <code>FJ</code> (the 100,000-meter square identifier)
Line 10:
For machine-readability and database storage, all spaces may be removed.
An MGRS grid reference 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> A ''grid square'' references a square or polygon on the Earth with a side length of 10 km, 1 km, 100 m, 10 m or 1 m, depending on the precision of the coordinates provided. (In some cases, squares adjacent to a Grid Zone Junction (GZJ) are clipped, so "polygon"
{| class="wikitable" style="text-align: left;"
|+ MGRS precision levels
! MGRS Coordinate
! Precision (side length)
|-
| <code>4Q FJ</code>
Line 36:
|}
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
Related to this is the primacy of the southwest corner of the
[[Google Maps]] recognizes MGRS grid references which have a one-meter square precision (10-digit numerical ___location) with spaces permitted only between the 100,000-meter square, the easting, and the northing: e.g., <code>4QFJ 12345 67890</code>. The mapping application returns a dropped pin representing the [[centroid]] of the area referenced.
==Grid zone designation==
[[File:Universal_Transverse_Mercator_zones.svg|thumb|300px|UTM zones on an equirectangular world map with irregular zones in red and New York City's zone highlighted]]
The first part of an MGRS coordinate is the ''grid-zone designation''. The 6° wide UTM zones, numbered 1–60, are intersected by latitude bands that are normally 8° high, lettered C–X (omitting I and O). The northmost latitude band, X, is 12° high. The intersection of a UTM zone and a latitude band is (normally) a 6° × 8° polygon called a ''grid zone'', whose ''designation'' in MGRS is formed by the zone number (one or two digits – the number for zones 1 to 9 is just a single digit, according to the example in DMA TM 8358.1, Section 3-2,<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> Figure 7), followed by the latitude band letter (uppercase). This same notation is used in both UTM and MGRS, i.e. the UTM grid reference system; the article on [[Universal Transverse Mercator]] shows many maps of these grid zones, including the irregularities for Svalbard and southwest Norway.
As Figure 1 illustrates, Honolulu is in grid zone 4Q.
Line 77 ⟶ 79:
One always reads map coordinates from west to east first (easting), then from south to north (northing). Common mnemonics include "in the house, up the stairs", "left-to-right, bottom-to-top" and "Read Right Up".
===Truncation, not rounding
As mentioned above, when converting UTM coordinates to an MGRS grid reference, or when abbreviating an MGRS grid reference to lower precision,
This However, truncation
Likewise, the civilian/continental version of MGRS, [[USNG]], ==Squares that cross a latitude band boundary==
Line 104 ⟶ 110:
*[[Ordnance Survey National Grid]] is another Transverse Mercator system designed for locations in the British Isles
*[[Irish Transverse Mercator]] has replaced the [[Irish grid reference system]]
*[[United States National Grid]] (USNG), developed by the [[Federal Geographic Data Committee]], is an implementation of MGRS for the United States and its possessions.
*[[World Geographic Reference System]] (GEOREF) has been used for air navigation, but is rarely seen today.
*[[Maidenhead Locator System]] is used by amateur radio operators.
|