重力场模型和DEM提高GPS高程转换精度

为了充分利用GPS观测数据中的高程信息，提高山区GPS大地高转换为正常高的精度，利用国内外最新的重力场模型和数字高程模型（DEM）数据，采用移去-拟合-恢复方法进行GPS高程转换，并与三等水准实测高程进行比较，结果表明：在地形起伏较大的山区，利用高精度的地球重力场模型，可将GPS高程转换的精度提高50%左右。地形改正也可以在一定程度上提高GPS高程转换的精度，地形对高程异常的影响与地形起伏程度和拟合点间高差有关。对于几何水准难以施测的山区利用GPS观测信息确定高精度海拔高程有重要意义。

THE GRAVITY FIELD MODEL AND DEM IMPROVING THE GPS ELEVATION CONVERSION ACCURACY

In order to fully utilize the elevation information of GPS observation date and to improve the precision of normal height of observation point that are converted from GPS ellipsoid height in mountainous area，the gravity field model and Digital Elevation Model（DEM）that are published recently are used to convert GPS elevation with the remove-match-restore method.The matched elevation is compared with that of three-grade leveling measure.The statistical results show that high-precision gravity field models can improve the accuracy of GPS elevation transformation up to 50% in mountainous area.In a certain extent，the terrain correction can improve the accuracy of GPS elevation conversion.The correction of elevation anomaly induced by terrain are relevant with undulation of terrain and elevation difference among GPS observation points.The conclusion is important to get high-precision normal elevation from the GPS observation information in mountainous area where the leveling is difficult to carry out.