Buliding Local Independent Coordinate System Model Based On CGCS2000and Analyzing Example

With the development of "digital city" project, research the transformation model ofmeasuring coordinate system, achieve rapid transformation and updated of the results ofsurveying and mapping all over the country, turn the original surveying and mapping’s resultsinto CGCS2000coordinates by loss of precision way,meet the needs of the digital cityconstruction; Analyze all kinds of elevation conversion method and achieve the effectivetransformation of elevation in the complex area in high altitude terrain; In the present andfuture, building2000local independent coordinate system for surveying and mapping workhas important theoretical significance and practical value. This paper is on the basis of GPScontrol network data in the prefecture of Guizhou province, building rigorous mathematicrelationship between CGCS2000ellipsoid and local ellipsoid, deducing differential equationof geodetic coordinate more closely, optimizing established method of local ellipsoid to solvethe problem of projection deformation in the high altitude mountainous terrain, building localcoordinate system based on CGCS2000to meet the needs of the city’s geographic space frameconstruction,The paper analyzes and deduces the method to eliminate the model error of coordinatetransformation, compares all kinds of fitting method of GPS elevation, discusses the functionrelationship between the parameters of the Geodetic coordinate differential equation,optimizes construction model of local coordinate system. The following conclusions:(1) The gravity process eliminates the model error which is caused by the unevendistribution of known points. The robust estimation process rules out the affect which possiblegross error make on the conversion accuracy of data and ensure the accuracy of coordinatetransformation of small angle. The article improves rotation matrix of seven parametersmodel with large angle by weakening the affect between correlation of spinning parametersand solution parameters, obtaining improved results obviously through experiments ofsimulation parameters under different angles. (2) Analyze practical of various elevation fitting model. Choosing height fitting methodmentioned in chapter3, it proves that BP neural network model has a better fitting effect.(3) Through the analysis of the geodetic coordinate differential equation, found thegeodetic coordinate differential equation is wrong which is in document [2] and document[8].The paper corrects it by combining the function relationship between ellipsoid parameterand deduce the geodetic coordinate differential equation again. Take an example of formula4.21, it has superior conversion accuracy of improved the geodetic coordinate differentialequation than the old geodetic coordinate differential equation.(4) Regarding CGCS2000ellipsoid as reference ellipsoid, optimization model of thetraditional local independent coordinate system and build local coordinate system based onCGCS2000coordinate system. Its maximum length deformation is2.0cm/km. Accuracy isless than2.5cm per km of local coordinate system stipulated in the urban measurementspecifications.Conclude chapter4about theory model of local coordinate system and exampleanalysis, building local independent coordinate system selects the ellipsoid expanding methodis better than the other two methods at high altitude mountainous area. Projection length hasminimum error and point has a little change. Taking an average of the peak is morereasonable than the other two methods when choose datum mark.