Rational choosing of projection zone and perspective plane based on GPS network of mining area

Lots of mining areas are far away from the national zone dividing prime meridians of three degree or located on high relief,which results in the fact that the side lengths of GPS control network is at variance with mining levels and the actual ground measures.Then it brings length projection distortion and makes the product of the network fail to meet the precision level of one to five hundred scale plotting,construction layout and laneway breakthrough.The paper analyzes theoretically the influence law of length distortion after the reductions from measured side length to reference ellipsoid surface and then from side length on the reference ellipsoid surface to gauss perspective plane.It also discusses theoretical methods to restrict and the projection distortion influence.It proposes idiographic schema to rationally choose projection zone and perspective plane.The choice of projection zone and perspective plane in the establishment of plane coordinate system of GPS network in Datong mining area has validated that the schema is feasible.