sea level datum

The influences of the short tidal data and the "higher sea level in the south and lower sea level in the north" are expounded. At the end, some ideas and suggestions are put forward for the new level system "85 National Datum Level".

阐述了引用潮汐资料过程与我国海面南高北低的影响，对新高程系“85国家高程基准”提出了意见与建议。

Height of gravity points that is height above sea level rather than ellipsoid height measured with GPS used in gravity survey in China was measured by method of ignoring height abnormity within a range of 50 km from datum mark.

GPS测量测得的是椭球高程，而我国重力测量求得的是水准高程。目前，野外工作中采用GPS基准站周围50km范围内忽略高程异常的办法进行重力测点高程的测量。

It briefly introduces the historical change of Wusong Datum in the Changjiang Estuary region, and analyzes the spatial variations of regional mean sea level and theoretical bathymetrical datum plane in this region. A discussion is also given to the height system of the Changjiang Estuary region.

简要介绍长江河口地区吴淞零点的历史沿革，分析了长江河口地区水域平均海水面、理论深度基准面的空间变化，进而讨论长江河口地区的高程系统。