Geoid Refinement Based On EGM2008,Residual Terrain Model And Ground Gravity Data

GPS measurement can provide accurate latitude-longitude and geodetic height which has the characteristic of fast,all-weather,requiring no intervisibility and so on.Normal height of the measuring points can be obtained by combining GPS measurement with quasi-geoid model whose measurement accuracy generally depends on two factors: one is the accuracy of geodetic heights measured by GPS measurement,and the other is the accuracy of the geoid undulation(height anomaly).With the development of GPS measurement technique and the improvement of measurement mode,high precision geodetic heights could be gained by ways of utilizing GPS receiver with IGS tracing station or using CORS system,so how to obtain the high precision geoid models became the key problem requiring resolved in GPS height measuring.This paper introduce the methods of residual terrain model recovering gravity field model high-frequency signal,inconsistent correctional method of model datum,the Stokes theory to determine the geoid undulation and the method of processing real gravity data according to the theory,specialty and computation of EGM2008 global geopotential model,which calculate the geoid difference with the method of “Remove-Restore”.Taking XingCheng Niangniang Temple and Jilin province as an example,we first calculate the inconsistent parameters of datum based on GPS real measuring data to correct geoid model,and then recovery the high-frequency signal of EGM2008 global geopotential model and make the gravitational geoid model based on residual terrain model and the method of “Remove-Restore”.In this paper,we evaluates the accuracy of the two methods which depends on real measuring data and proposes the way to refine geoidal surface synthesizing remaining ground model and the measuring gravity data.Cubic spline interpolation,Inverse distance weighing(IDW),quadratic curved surface fitting method were used to compare and analyze their calculation results while utilizing synthetic approach to fit residual error.At last,accuracy assessment and correction effect of all the methods was conducted and analyzed to determine the best correction solution according to the GPS and leveling data of study area and the location,terrain and extent of different areas.The results indicate that the accuracy of corrected EGM2008 model which utilized the residual terrain model is 1 cm higher than original model while utilizing gravity data is about 2.5 cm higher whose accuracy and reliability both higher than RTM model in the study area of Niangniang Temple.What is more,the accuracy of corrected EGM2008 model by the residual terrain model was somewhat better.The correction effects significance is positively associated with terrain complexity of study area of the remaining ground model.Utilizing gravity geoid calculated by real measuring gravity data to fit residual error for correction results can the regional error of this model and improve the accuracy.