Military Grid Reference System: Difference between revisions

Revision as of 16:37, 4 September 2020

Revision as of 22:53, 11 February 2022

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* In the alternative ''AL scheme'',<ref name="MGRS_Final_Guidance"/> also known as ''MGRS-Old'',<ref name="Military_Map_Reading_201"/> which is used for some older [[datum (geodesy)|geodetic datum]]s, the row letters are shifted 10 steps in the alphabet. This means that the letter for the first row is L in odd-numbered zones and R in even-numbered zones. The westmost square in the first row, in zone 1, has identification AL.

If an MGRS coordinate is complete (with both a grid zone designation and a 100,000 meter square identification), and is valid in one lettering scheme, then it is usually invalid in the other scheme, which will have no such 100,000 meter square in the grid zone. (Latitude band X is the exception to this rule.) Therefore, a position reported in a modern [[datum (geodesy)|datum]] usually can notcannot be misunderstood as using an old datum, and vice versa – provided the datums use different MGRS lettering schemes.

In the map (figure 1), which uses the AA scheme, we see that Honolulu is in grid zone 4Q, and square FJ. To give the position of Honolulu with 100&nbsp;km resolution, we write 4QFJ.