The Conversion Between Gauss Projection And Direction Arbitrary Projection

According to the "Specification for survey engineering of High-speed Railway",the engineering independent coordinate system should be adopted in the plane coordinate system of high-speed railway engineering survey,and the deformation value of the projection length of the plane coordinate system on the projection elevation surface of the railline surface should not exceed 10 mm / km.In order to meet the requirements of the limit difference,the railway design department generally uses Gauss projection to project the line plane into several engineering independent coordinate systems with overlapping bands.This projection method can meet the limit difference requirement in a certain bandwidth,but for the high-speed railway with long and long lines,too many zoning can easily cause the redundancy of data and the problem of excessive lateral deviation in the process of overlapping band lap.In order to better meet the precise requirements of projection mode and data processing for high smoothness of high speed railway track,some scholars have proposed to use directional arbitrary projection method to project the whole railway line.Directional arbitrary projection is a kind of projection mode similar to oblique axis Mercator projection.Its basic theoretical idea is to use the parameters of the earth ellipsoid and fit the projection center line with the control points of the measuring area to carry on the projection in the range of the measuring area.According to the direction of the trackline,the projection center line can be optimized automatically.This projection method can make thousands of kilometers of railway lines use only one projection belt,which completely solves the adverse effects of too many Gauss projection belts on railway lines.The direction adaptive projection is based on the same projection elevation plane projection for the whole long railway line.The single-valued plane coordinate system is unified by this projection method.In this paper,based on the existing directional arbitrary projection theory,the method of four-parameter transformation is adopted.The transformation of intersection points coordinates between Gauss projection and direction arbitrary projection is realized,and curve synthesis elements are corrected considering the influence of different projection plane height.The transformation relationship between slope table elements in Gauss projection coordinate system and direction arbitrary projection coordinate system is derived.Based on the direction arbitrary projection,the conversion relationship between the plane mileage and the orbital space mileage of the point of gradient change and the arbitrary track detection point is derived.Finally,the related functions of the conversion between directional arbitrary projection and Gauss projection coordinate and mileage are realized by programming.The correctness of the software algorithm is verified by a concrete engineering example,and the directional arbitrary projection based on the same projection elevation surface is compared with the Gaussian projection.The advantages of directional arbitrary projection using single-valued plane coordinate system in data processing and operation and maintenance management are proved.