Here is what the ArcView Help file has to say about UTM (Universal Transverse Mercator): UTM - For the Universal Transverse Mercator System, the globe is divided into sixty zones, each spanning six degrees of longitude. Zones are numbered from west to east starting at 180° longitude (the mid Pacific Ocean). Each zone has its own central meridian. This projection is a specialized application of the Transverse projection. The limits of each zone are 84° N, 80° S. Method of projection - Each UTM zone has its own central meridian from which it spans 3 degrees west and 3 degrees east of that central meridian. The cylindrical methodology is the same as that for the Transverse projection. Note that the position of the cylinder rotates systematically around the globe. X- and y-coordinates are recorded in meters. The origin for each zone is the Equator and its central meridian. To eliminate negative coordinates, the projection alters the coordinate values at the origin. The value given to the central meridian is the false easting, and the value assigned to the Equator is the false northing. For locations in the Northern Hemisphere, the origin is assigned a false easting of 500,000, and a false northing of 0. For locations in the Southern Hemisphere, the origin is assigned a false easting of 500,000 and a false northing of 10,000,000. Lines of secancy - Two lines parallel to and approximately 180 km to each side of the central meridian of the UTM zone. Linear graticules - The central meridian and the Equator. Properties Shape - Conformal. Accurate representation of small shapes. Minimal distortion of larger shapes within the zone. Area - Minimal distortion within each UTM zone. Direction - Local angles are true. Distance - Scale is constant along the central meridian, but at a scale factor of 0.9996 to reduce lateral distortion within each zone. With this scale factor, lines lying 180 km east and west of and parallel to the central meridian have a scale factor of 1.0. Limitations - Designed for a scale error not exceeding 0.1 percent within each zone. This projection spans the globe from 84° N to 80° S. Error and distortion increase for regions that span more than one UTM zone.   Projections