Universal polar stereographic coordinate system
The universal polar stereographic (UPS) coordinate system is used in conjunction with the
In the polar regions, directions can become complicated, with all geographic north–south lines converging at the poles. The difference between UPS
Projection system
As the name indicates, the UPS system uses a stereographic projection. Specifically, the projection used in the system is a secant version based on an elliptical model of the earth. The scale factor at each pole is adjusted to 0.994 so that the latitude of true scale is 81.11451786859362545° (about 81° 06' 52.3") North and South. The scale factor inside the regions at latitudes higher than this parallel is too small, whereas the regions at latitudes below this line have scale factors that are too large, reaching 1.0016 at 80° latitude.
The scale factor at the origin (the poles) is adjusted to minimize the overall distortion of scale within the mapped region. As with the Mercator projection, the region near the tangent (or secant) point on a Stereographic map remains very close to true scale for an angular distance of a few degrees. In the ellipsoidal model, a stereographic projection tangent to the pole has a scale factor of less than 1.003 at 84° latitude and 1.008 at 80° latitude. The adjustment of the scale factor in the UPS projection reduces the average scale distortion over the entire zone.
References
- Snyder, John P. (1987). Map Projections – A Working Manual. U.S. Geological Survey Professional Paper 1395. United States Government Printing Office, Washington, D.C.
- Defense Mapping Agency Technical Manual 8358.1 Datums, Ellipsoids, Grids, and Grid Reference Systems (PDF). Defense Mapping Agency. 1990.
- TM8358.2: The Universal Grids: Universal Transverse Mercator (UTM) and Universal Polar Stereographic (UPS) (PDF). Defense Mapping Agency. 18 September 1989. Retrieved 7 March 2010.
External links
- National Geospatial-Intelligence Agency, Geospatial Sciences Publications
- GeographicLib provides a utility GeoConvert (with source code) for conversions between geographic, MGRS. Here is an online version of GeoConvert.