Editing Military Grid Reference System (section)

==Polar regions==
[[Image:MGRSgridSouthPole.png|thumb|Figure 3. The MGRS grid around the South Pole.]] 

[[Image:MGRSgridNorthPole.png|thumb|Figure 4. The MGRS grid around the North Pole.]] 

In the polar regions, a different convention is used.<ref name="Appendix_B">[http://earth-info.nga.mil/GandG/publications/tm8358.1/tr83581f.html DMA Technical Manual 8358.1, Appendix B.] Datums, Ellipsoids, Grids, and Grid Reference Systems.</ref>  South of 80°S, UPS South ([[Universal Polar Stereographic]]) is used instead of a UTM projection.  The west half-circle forms a grid zone with designation A; the east half-circle forms one with designation B; see figure 3.  North of 84°N, UPS North is used,  and the west half-circle is Y, the east one is Z; see figure 4.  Since the letters A, B, Y, and Z are not used for any latitude bands of UTM, their presence in an MGRS coordinate, with the omission of a zone number, indicates that the coordinates are in the UPS system. 

The lettering scheme for 100,000&nbsp;m squares is slightly different in the polar regions.  The column letters use a more restricted alphabet, going from A to Z but omitting D, E, I, M, N, O, V, W; the columns are arranged so that the rightmost column in grid zone A and Y has column letter Z, and the next column in grid zone B or Z starts over with column letter A.  The row letters go from A to Z, omitting I and O.  The restricted column alphabet for UPS ensures that no UPS square will be adjacent to a UTM square with the same identification.

In the polar regions, there is only one version of the lettering scheme.<ref name="Appendix_B"/>