Origins of the Military Grid Reference System


Several weeks ago John Carnes, owner of the Maptools.com website, contacted me with some additional information regarding the origins of the Military Grid Reference System (MGRS). It appears John has a friend who had some interest in the origins of MGRS and back in 1994 contacted the Defense Mapping Agency looking for information.

John Hager, a geodesist with DMA, responded with a detailed letter and references tracing the history and origins of MGRS. John Carnes has taken this information and created a very informative page on his website. I encourage you all to go to John’s MGRS history page and read up on the history of MGRS and review the links he provides. There’s a lot of great historical information there!

Some points and observations I gleaned from reviewing the documents:

  • The Universal Transverse Mercator Grid system (UTM) was developed far earlier than I thought. Based on my previous reading I thought that UTM had been developed by the Army Map Service specifically to support the development of a world-wide grid reference system like MGRS. However, it appears that the U.S. Army adopted UTM in 1937, years before the creation of the Army Map Service.
  • The original MGRS structure as proposed in 1948 had it covering globe in an area from 80° north latitude to 80° south latitude. Above and below 80° the polar regions were to be covered using the Universal Polar Stereographic (UPS) coordinate system. However, some time after 1948 the MGRS coverage was extended to cover up to 84° north latitude. MGRS was extended into this region as a reflection of NATO’s anticipation of having to fight a ground war with the Soviet Union in arctic regions.
  • There’s a lot of concern expressed by a lot of people in these documents regarding grid zone intersections, or ‘zippers’ as we referred to them. Everyone understood these grid zone intersection areas posed critical challenges and demanded extra caution when directing operations that crossed an intersection boundary. In fact, the issue so concerned the British that they expressed a preference for a less accurate ‘mesh’ grid system that would eliminate grid zone intersections altogether. One of the reasons UTM was selected as the foundation to build MGRS on is because its narrower 6° wide zones introduced less error in these intersection areas.
  • As good as the UTM/MGRS system was (and still is) the fact that it had to be built on ‘local’ datums like NAD27 (in the US), ED50 (in Western Europe) or the Tokyo Datum (in Korea) quickly revealed the need for a world-wide datum, one that was equally good (or as one of my survey instructors put it, “equally poor”) across the globe. This need led directly to the World Geodetic System of 1984, or WGS84, the datum on which all US and NATO military maps are currently based.

So put your geo-geek cap on, head over to John’s website and read up on the origins of MGRS. These documents outline the background of the grid system many of us have a love-hate relation with, yet it’s a grid system that has stood the test of time in places like Europe, Korea, Vietnam, Kuwait, Iraq and Afghanistan, and is now adopted for official use here in the United States as the US National Grid.

– Brian

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