Method for Calculating Transformation Parameters by Way of Integrating GPS Data Observed in Different Periods

This paper puts forward a method for calculating three-dimensional coordinate transformation parameters with the integrated GPS data observed in different periods.The main idea is that the transformation parameters denote the relationship between two coordinate systems.If the datum points of two coordinate systems keep unchanged and the coordinates of the GPS control points in two systems are observed from the corresponding datum points almost at the same time,the calculated transformation parameters also keep unchanged even the coordinates of these control points may change at different time if they are not stable.In the sedimentary land as Shanghai,the heights change much more quickly than plane coordinates due to the subsidence of land surface.Because the control points with plane coordinates and the bench marks with normal height are normally set in different points in urban control net,this paper derives the corresponding model to separate the plane coordinate and height in the transformation model.