Geoid Refinement Based On Land Gravity And GPS/leveling Data In Xingcheng Geophysical Survey Test Area

We can directly get the orthometric/normal height of the survey point combinesthe GPS survey with the regional (Quasi) geoid model.GPS technology widespreadused in Geophysical Survey because of its advantages. In the geophysical survey,especially in the large scale geophysical survey the requirement of the heightprecision is very high. The precision of GPS height measurement is decided by theprecision of GPS survey and the geoid model. The key issue of GPS heightmeasurement used in the geophysical is to build the regional high precision geoidmodel.This article introduced the stokes theory which can decided the geoidalundulation, the global high precision EGM2008gravity model, gravity dataprocessing and the refine methods of regional geoid. We take Xingcheng geophysicalsurvey test area of Jilin University as a case, built the regional geometric methodgeoid model and hybrid method geoid model of Xingcheng geophysical survey testarea of Jilin University with GPS leveling geometric method and hybridmethod, using land gravity data, EGM2008and GPS/leveling data. Compare theprecision of different geometric method models, using different density of controlpoints. We also compared the precision of different models with different methodswhen refining residual geoid model, in this article we used the QSF,MC,IDW,CS andLsc5methods to refine the residual geometric geoid model. This article computed theprecision of models using the independent GPS/leveling points of the test area as thecheck points. The precision between the geometric method model and the hybridmethod model were compared, and the applicability of this method used ingeophysical prospecting survey was analyzed.The result indicated that in the geometric models the cubic spline interpolationhas the highest precision and stability. The moving curve fitting and least square collocation also have high precision and stability.The quadratic surface fitting has thelowest precision and the inverse distance weighting interpolation has the loweststability. The precision and the stability increased with the density of the controlpoints. The precision of hybrid method model also depends on the refinement methodof residual geoid, the RMS of the Moving curve fitting method is twice as large as theQSF method. The precision and reliability of Hybrid method model were higher thanthe geometric method model as the hybrid method model considered the variation ofthe geoidal undulation.When the mean interval of calculating points is3km,the precision of the geoidmodels is from±1.2cm to±3.8cm, Both of the two refined geoid models can reachthe accuracy of centimeter order also can meet the requirement of large scalegeophysical survey.When the mean interval of calculating points is20km, The precision of the geoidmodel which based on EGM2008gravity model is less than±0.1m and whencalculated with single GPS/leveling point the precision of the refined model is±14cm.The result indicated that the regional EGM2008geoid model refining method ofusing single GPS/leveling point can completely met the requirements of physicalpoints height measurement in petroleum geophysical prospecting with different scalesand geophysical survey small scale.