全球或区域性高程基准面的统一始终是大地测量学研究的主要内容之一，对于构建“数字区域”和“数字地球”及研究全球或区域性环境变化具有重要的科学意义和现实意义。本文利用全球重力场模型EGM96和WDM94及GPS水准数据，确定了香港主要高程基准面与我国1956黄海高程基准面的重力位差。计算结果表明，这两个基准面的重力位差为（8.366±0.765）m2s，表明香港主要高程基准面平均低于我国1956黄海高程基准面（0.855±0.078）m2s。本文的计算结果有助于本地区高程基准面的统一。

介绍了香港大地水准面HKGEOID-2000和深圳市高分辨率、高精度似大地水准面SZGEOID-2000。利用HKGEOID-2000和GPS椭球高求得的正常高与香港地区由三角高程测量得到的“正常高（或本地高）”进行比较，结果表明,其差值的均方根为0.102m，标准差（STD）为±3.4cm。结合HKGEOID-2000、SZGEOID-2000和这两个大地水准面模型重复覆盖地区的高精度GPS水准数据，探测这两个大地水准面模型之间的差异和香港主要高程基准面（HKPD）与我国1956黄海高程基准面之间的系统偏差。

以计算香港大地水准面为例，着重研究了以下几点：①DTM的分辨率对地形改正的影响；②质量柱体地形模型与质量线地形模型对计算地形改正的差异；③采用Helmert凝聚改正法，计算地形对大地水准面的间接影响；④比较经典Stokes-Helmert方法与Sjoberg方法计算地形对大地水准面的影响。

To select the best geo-potential model for the determination of Hong Kong and Shenzhen local geoids, three models-EGM96, WDM94 and GPM98CR-were tested in the region using GPS/leveling data and gravity measurements. The data include GPS/leveling observations at 43 stations, 640 gravity measurements covering the whole territory of Hong Kong, and 62 high precision GPS/leveling observations and 4870 gravity observations in Shenzhen. The results show that the geoid undulations from these geo-potential models contain systematic errors both in Hong Kong and in Shenzhen. After the biases are removed using GPS/leveling data, the STD of geoid undulation differences for EGM96, WDM94 and GPM98CR are 0.039m, 0.037m and 0.030m respectively in Hong Kong, and 0.052m, 0.032m and 0.095m in Shenzhen. While the STD of gravity anomaly differences for EGM96, WDM94 and GPM98CR are 14.136mGal, 13.559mGal and 15.130mGal respectively in Hong Kong, and 8.815mGal, 8.545mGal and 11.567mGal in Shenzhen, it is clear that the WDM94 model is the best of the three.