Research Of GPS Data Processing Method For High Precision Ground Control

In the progress of establishing high precision GPS ground control network, a usual method is carried out to lessen the length distortion of projection. The method is to select the central longitude as the central meridian and the average normal height as the projection elevation of Gauss projection. However, the method doesn't work well in some long line control network. In the basis of theoretical research, a new GPS division projection method is proposed and is proved with a few experiments.Firstly, the coordinates conversion models between space right-angle coordinates, geodetic coordinate and Gauss planar coordinates are introduced. Secondly, GPS network's 2D and 3D adjustment is presented in details, and the computational methods using GPS datum and ground datum to establishing high precision engineering control-network is given. Finally, in order to verify the validity of the new method, a GPS control network of the Guangyuan-Sanhuiba section of the Lanyu railway is taken as an example. And the comparison of the results calculated by the usual way and the new method is made.Compared with the results, two conclusions can be drawn. 1. The direction of baselines can be kept uniform on condition that adopting the same central meridian and different projection elevations of Gauss projection. 2. The division projection method can fit the projection length as its actual length well, and the direction can be coincident with traditional ways.