Universal Transverse Mercator (UTM) Grid Zones 31N thru 37N differ from the standard 6° wide by 84° zone for the northern hemisphere, in part to accommodate the southern half of the Kingdom of Norway. The scale is less than 1 inside the standard lines and greater than 1 outside them, but the overall distortion is minimized. In each zone the scale factor of the central meridian reduces the diameter of the transverse cylinder to produce a secant projection with two standard lines, or lines of true scale, about 180 km on each side of, and about parallel to, the central meridian (Arc cos 0.9996 = 1.62° at the Equator). Distortion of scale increases to 1.0010 at the zone boundaries along the equator. By using narrow zones of 6° of longitude (up to 668 km) in width, and reducing the scale factor along the central meridian to 0.9996 (a reduction of 1:2500), the amount of distortion is held below 1 part in 1,000 inside each zone. The polar regions south of 80°S and north of 84°N are excluded.Įach of the 60 zones uses a transverse Mercator projection that can map a region of large north-south extent with low distortion. Zone 1 covers longitude 180° to 174° W zone numbering increases eastward to zone 60, which covers longitude 174☎ to 180°. The UTM system divides the Earth into 60 zones, each 6° of longitude in width. Simplified view of contiguous US UTM zones, projected with Lambert conformal conic. This projection is conformal, which means it preserves angles and therefore shapes across small regions. The transverse Mercator projection is a variant of the Mercator projection, which was originally developed by the Flemish geographer and cartographer Gerardus Mercator, in 1570. In the post-war years, these concepts were extended into the Universal Transverse Mercator/ Universal Polar Stereographic (UTM/UPS) coordinate system, which is a global (or universal) system of grid-based maps. Calculating the distance between two points on these maps could be performed more easily in the field (using the Pythagorean theorem) than was possible using the trigonometric formulas required under the graticule-based system of latitude and longitude. Prior to the development of the Universal Transverse Mercator coordinate system, several European nations demonstrated the utility of grid-based conformal maps by mapping their territory during the interwar period. For different geographic regions, other datum systems can be used. The World Geodetic System WGS84 ellipsoid is now generally used to model the Earth in the UTM coordinate system, which means current UTM northing at a given point can differ up to 200 meters from the old. 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.
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