椭球与投影(国外英文资料).doc

椭球与投影(国外英文资料) Frame definition and transformation in GIS Author: hard work?? Source: computer world news ? ????? Since the Mapinfo GIS system development is published in the computer world online after, there are several readers asked me coordinate system definition and transformation problems, question boils down to (1) on the Mapinfo map very well, but in the MapX display not to come out or not; (2) how the GPS coordinates of WGS84 are transferred to the 54 coordinates map of Beijing. These problems also had confused me, here I talk about my personal experience, some understanding and reference for readers, and also hope that the relevant professionals to give correct and supplement. Ellipsoid, datum, and map projection The frame definition in GIS is the basis of GIS system. It is very important to define the coordinate system of GIS system correctly. Coordinate system defined by the Datum of GIS and map Projection two set of parameters, and the definition of Datum by certain Ellipsoid and its corresponding conversion parameters, GIS system is to define the coordinate system, therefore, you must first make clear the earth Ellipsoid, Ellipsoid, a Datum (Datum) and map Projection, the Projection of the three basic concepts and the relationship between them. Datum is the use of specific ellipsoid to certain areas of the earths surface approximation, so each country or region has its own datum, we usually appellation of the 54 Beijing coordinate system 80, xi an actually refers to the two the datum of our country. With reference to the former Soviet union in China since 1953 using carat SuoFuSi basis (Krassovsky) ellipsoid set up Beijing 54 coordinate system in our country, in 1978 by the international association of geodesy recommended 1975 earth ellipsoid established the new China geodetic coordinate system, xian coordinate system 80, the geodetic remains largely to Beijing 54 coordinate system as a reference, Beijing 54 and 80 xi an coordinate conversion between c