The main difficulty is that for ease of calculation you'd like a cartesian grid, which maps poorly to the spheroid shape of the earth. One solution is UTM https

The main difficulty is that for ease of calculation you'd like a cartesian grid, which maps poorly to the spheroid shape of the earth. One solution is UTM https://en.wikipedia.org/wiki/Universal_Transverse_Mercator_coordinate_system https://en.wikipedia.org/wiki/Universal_Transverse_Mercator_... which divides the earth into 60 zones, and then inside each zone you have a cartesian grid with meters as the unit. So a UTM coordinate consists of the zone designator, and then distances in meters from the equator and the zone's central meridian. There also MGRS https://en.wikipedia.org/wiki/Military_Grid_Reference_System https://en.wikipedia.org/wiki/Military_Grid_Reference_System , the NATO military variant of UTM.