The determination of an accurate national geoid model remains one of the main challenges of geodetic research projects in Ethiopia. The main aim of this study is to develop a new gravimetric geoid model, named the ETH–GM21, over Ethiopia. This new geoid model is based on a combination of terrestrial and airborne gravity data together with the state-of-the art combined Global Geopotential Model (GGM) and the high-resolution SRTM3 (Shuttle Radar Topography Mission with a spatial resolution of 3 arc-second) global digital elevation model. The ETH–GM21 has been determined using the remove-compute-restore (RCR) procedure and the least–squares collocation method. The accuracy of ETH–GM21 gravimetric geoid model has been evaluated using geometric geoid heights obtained from GNSS (Global Navigation Satellite Systems) and levelling data distributed over the country. On the basis of this evaluation the estimated accuracy of geoid heights from the ETH–GM21 geoid model is at the level of 13 cm. The ETH–GM21 can be recommended as a first relatively accurate vertical reference surface for a definition of heights within the whole Ethiopia.

确定准确的国家大地水准面模型仍然是埃塞俄比亚大地测量研究项目的主要挑战之一。本研究的主要目的是在埃塞俄比亚上空开发一种新的重力大地水准面模型，命名为 ETH-GM21。这种新的大地水准面模型基于地面和机载重力数据以及最先进的全球地势模型 (GGM) 和高分辨率 SRTM3（空间分辨率为 3 弧度的航天飞机雷达地形任务）的组合。第二）全球数字高程模型。ETH-GM21 已使用移除-计算-恢复 (RCR) 程序和最小二乘搭配方法确定。已使用从 GNSS（全球导航卫星系统）获得的几何大地水准面高度和分布在全国的水准数据评估了 ETH-GM21 重力大地水准面模型的准确性。在此评估的基础上，ETH-GM21 大地水准面模型的大地水准面高度估计精度为 13 厘米。可以推荐 ETH-GM21 作为第一个相对准确的垂直参考面，用于定义整个埃塞俄比亚的高度。