A Method to Improve the Accuracy of Plane Coordinate Conversion Between Different Benchmarks
In order to improve the precision of plane coordinate conversion between different datum,a four-parameter coordinate conversion method which calculated the approximate parameters of coordinate system first was adopted.The main steps of the method are as follows:Firstly,by studying the Gaussian projection deformation and the principle of compensating coordinate system,the linear correlation between the height of the projection surface and the length deformation of the coordinate transformation control point was analyzed.Then,combined with the influence of Gaussian projection on the angular projection deformation,the coordinate transformation model with scale parameters and rotation parameters was determined to reduce the linear projection deformation difference between control points,such as the four-parameter and seven-parameter transformation model.Secondly,by analyzing the influence of ellipsoid type on the projection deformation difference between coordinate transformation control points,a method which calculating the approximate parameters of different ellipsoid coordinates was proposed to reduce the Gaussian projection nonlinear deformation difference.The research results show that,the effect of ellipsoid type on the nonlinear projection deformation of coordinates is submillimeter.When the coordinate system parameters of different datum are approximately the same,the inner and outer coincidence accuracy of the coordinate transformation of four parameters and seven parameters can reach millimeter level.An engineering example shows that the precision of coordinate transformation can be improved by one order of magnitude by the four-parameter coordinate conversion method which calculates the approximate parameters of coordinate system first.
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