The UTM system divides the world into a regular nonoverlapping grid of quadrangles, called zones, each 8 by 6 degrees in extent. Each zone uses formulas for a transverse version of the Mercator projection, with projection and ellipsoid parameters designed to limit distortion. The Transverse Mercator projection is defined between 80 degrees south and 84 degrees north.
Beyond these limits, the Universal Polar Stereographic (UPS) projection applies. The UPS
has two zones only,
south, which also have
special projection and ellipsoid parameters.
In addition to the zone identifier—a grid reference in the form of a number
followed by a letter (e.g.,
31T)—each UTM zone has a false
northing and a false easting. These are offsets (in meters)
that enable each zone to have positive coordinates in both directions. For UTM, they are
constant, as follows:
False easting (for every zone): 500,000 m
False northing (all zones in the Northern Hemisphere): 0 m
False northing (all zones in the Southern Hemisphere): 10,000,000 m
For UPS (in both the
south zones), the
false northing and false easting are both 2,000,000.