地面重力数据结合GPS/水准数据精化兴城物探实验区大地水准面

区域大地水准面的确定是GPS测量常需解决的问题。目前确定大地水准面的方法主要包括重力法、GPS水准几何法及组合法,其中组合法因其精度和可靠性都较高,常用于计算高精度区域大地水准面。高精度的大地水准面模型是组合法确定区域大地水准面的关键。在我国,EGM2008全球重力场模型精度和分辨率均高于此前的所有模型,研究基于该模型的组合法大地水准面精化具有重要的实践意义。笔者以吉林大学兴城教学实习基地物探实验区为例,基于实测重力数据、EGM2008重力场模型和GPS水准数据,采用组合法精化了区域大地水准面,比较了组合法大地水准面模型和无重力实测数据的几何法大地水准面模型的精度差异,分析了该方法在物探测量中的适用性。结果表明,实验区组合法大地水准面模型精度最高达到1.2cm,并且误差分布区间较小,总体上精度和可靠性高于对比的几何方法,并且组合法和几何法获取的两种大地水准面模型均能满足大比例尺物探测量要求。EGM2008模型精度较高,故平坦地区使用组合法时,高密度的实测重力数据可能带来高频扰动,有可能降低EGM2008重力场模型本身的精度,所以重力数据采集过程中要顾及重力点的密度和空间分布。本文方法更适用于地形复杂的地区。

Geoid Refinement Based on Land Gravity and GPS/Leveling Data in Xingcheng Geophysical Survey Test Area

The local geoid fluctuation is the major problem for the application of GPS survey. Algorithm for refining local geoid includes gravity method,GPS leveling method,and hybrid method. Hybrid method is widely applied due to its high precision and resolution,while high precision earth gravity model is the key for the hybrid method.The precision and resolution of EGM2008 earth gravity model is much higher than any gravity model in China.The study on its application for the refinement of local geoid has an important practical significance.We refined the geoid of the Xingcheng geophysical survey test area of Jilin University by means of hybrid method model (HMM),with using land gravity data,EGM2008,and GPS/leveling.The precision between the HMM and the model is refined by geometric method without comparision with the land gravity data(GMM).Both of the applicability of this method and EGM2008 are analyzed.The results indicate that the maximum precision of HMM in the test area is 1.2 cm with a minimum error distribution interval,and both of the precision and reliability of HMM are higher than the GMM in varied topography.High density gravity data in a much plane area may produce a high frequency disturb to EGM2008 because of its high precision,and this disturb may decrease the precision of EGM2008,which means that the spatial distribution of gravity data survey needs to be emphasized.The geoid refinement method reported in this article may be much more suitable for a complex topographic area.