Application of Ellipsoid Expansion Method in the Establishment of Linear Engineering Coordinate System
[Purposes]This paper applies ellipsoid expansion method to establish the coordinate system of line engineering,and reduce the projection deformation caused by large span,high elevation,and high undulation in the survey area.[Methods]The principles of five ellipsoid expansion methods are dis-cussed,and the calculation and analysis are carried out from three aspects,namely,the amount of change in the long semi-axis,the amount of change in the geodetic coordinates of the base point,and the amount of deformation of the side length combing with examples.[Findings]The five ellipsoidal expansion meth-ods have different degree of rigour and the calculation results obtained are different,the results obtained by direct method,prime unitary curvature radius method and mean radius of curvature method have large differences,and the results obtained by planar analytic method and generalized differential method have the smallest differences,and the projection deformation amount can satisfy the requirements.[Conclu-sions]All five ellipsoid expansion methods can be used for the establishment of line engineering coordi-nate system.
ellipsoid expansion methodprojection deformationengineering coordinate system
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