基于EGM2008模型的GPS高程转换法

GPS求得的高程是地面点在WGS84坐标系中的大地高，而我国采用正常高系统的高程，是通过该点的大地高减去该点的高程异常获得。高程异常的获取，惯用的做法是曲面拟合法，这种方法在水准点稀少的测区（特别是山区）实施起来比较困难。EGM2008模型是迄今为止分辨率最高、精度最好、阶次最多的全球重力场模型。首先利用EGM20081′×1′的大地水准面模型计算各点的高程异常，再通过联测一个一等水准点，获取EGM2008模型所表示的全球似大地水准面与我国高程基准面之间的差异，即可将GPS大地高转换为1985国家高程基准的正常高。兴城测区实例表明，EGM2008模型高程转换法在山区仅用一个水准点即可实现GPS大地高到正常高的转换，且高效率、高精度。

GPS Elevation Conversion Based on EGM2008 Model

The elevation from GPS is geodetic height of surface point in WGS 84 coordinate system, while elevation we used in China is from normal height system obtained through the point＇ s geodetic height subtracts height anomaly. The habitual way to get height anoma- ly is surface fitting, the execution of the method in benchmark rare area （especially mountain area） is rather difficult. The EGM2008 model is a global gravity field model with highest resolution, best precision, and maximum order so far. Using EGM2008 1＂~ 1＂ geoid model to compute each point＇ s model height anomaly, through conjunction of a first order benchmark, obtains EGM2008 model repre- sented difference between global quasi-geoid and Chinese elevation datum, then able to convert GPS geodetic height into normal height of the National Vertical Datum 1985. The case study of Xingcheng survey area has shown, in mountain area, the EFM2008 mod- el elevation conversion only use one benchmark can realize conversion of GPS height into normal height with high efficiency and high precision.