The Universal Transverse Mercator System

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, north and 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 north and south zones), the false northing and false easting are both 2,000,000.

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