Research On Key Issue Of The High-Precision Quasi-geoid Determination

The geoid of High precision and high resolution areas not only provided the basis message of the earth spatial for the research and application on Surveying and mapping engineering, geodynamics,oceanography and earth science, but also supplied with high precision elevation datum for building the "digital China" and "digital area" and "digital city" system. In high precision quasigeoid refinemented,usually use a densely populated area of the calculation gravity spot results, and high precision, high resolution digital elevation model, gravity field model (EGM96, WDM94, IGG05B) that not below360levels, distributed uniformly, good reality GPS leveling measurement results, take use of the gravity methods and remove-recovery technologies to finish. During establishing high precision, high resolution quasigeoid, the accuracy of the topographic data, gravity materials, GPS leveling materials has played a decisive role.This paper introduced the basic theories and methods of refine local geoids; summarized the factors which influenced the precision of the quasigeoid such as the grid gravity anomaly error,GPS level data, multi-source data and so on; introduced the terrain reduction principle of constant density and variable density, analysised the influence of the DEM resolution to topographic-correcting and geoid by trial method.In addition, gave the further decomposition to the series of Molodensky, derived the formula of the effectors of the abnormal height of topographic, and combined with engineering examples on the analysis, the results showed that, for the abnormal height in plain of second order,there’s a little influence can be neglected, only need to consider the influence of ζ11; but in the areas of abnormal height mountains of second order influence is bigger, ζ120and ζ2can reach0.338m and0.133m respectively. Based on this, the high-precision, high-resolution regional geoid should be noted that some of the issues discussed, and on this basis to draw some useful conclusions and recommendations.