![]() ![]() For the remaining areas of Earth, including Hawaii, the International Ellipsoid was used. For areas within the contiguous United States the Clarke Ellipsoid of 1866 was used. From 1947 onward the US Army employed a very similar system, but with the now-standard 0.9996 scale factor at the central meridian as opposed to the German 1.0. It was probably carried out by the Abteilung für Luftbildwesen (Department for Aerial Photography). However, a series of aerial photos found in the Bundesarchiv-Militärarchiv (the military section of the German Federal Archives) apparently dating from 1943–1944 bear the inscription UTMREF followed by grid letters and digits, and projected according to the transverse Mercator, a finding that would indicate that something called the UTM Reference system was developed in the 1942–43 time frame by the Wehrmacht. The National Oceanic and Atmospheric Administration (NOAA) website states that the system was developed by the United States Army Corps of Engineers, starting in the early 1940s. UTM zones on an equirectangular world map with irregular zones in red and New York City's zone highlighted History ![]() The scale factor at the central meridian is specified to be 0.9996 of true scale for most UTM systems in use. Most zones in UTM span 6 degrees of longitude, and each has a designated central meridian. The parameters vary by nation or region or mapping system. The projection from spheroid to a UTM zone is some parameterization of the transverse Mercator projection. Specifying a location means specifying the zone and the x, y coordinate in that plane. However, it differs from global latitude/longitude in that it divides earth into 60 zones and projects each to the plane as a basis for its coordinates. Like the traditional method of latitude and longitude, it is a horizontal position representation, which means it ignores altitude and treats the earth surface as a perfect ellipsoid. The Universal Transverse Mercator ( UTM) is a map projection system for assigning coordinates to locations on the surface of the Earth. ![]()
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