The height datum problem and the role of satellite gravity models
The height datum problem and the role of satellite gravity models
复制标题
高度基准问题和卫星重力模型的作用
DOI：
10.1007/s00190-012-0574-3
复制
发表时间：
2012
影响因子：
4.4
通讯作者：
G. Venuti
中科院分区：
文献类型：
--
作者：
A. Gatti;M. Reguzzoni;G. Venuti
区域高度系统不涉及一个共同的等势面，如大地水准面。它们通常是参考潮汐计的平均海平面。由于平均海平面因地而异，因洲而异（±1至2米），每个验潮仪相对于一个共同参考面都有未知的偏差，这就是高程基准问题所涉及的确定。本文结合卫星重力任务数据的可获得性来讨论这一问题。由于偏高进入到地球重力异常的计算中，而地球重力异常又用于大地水准面确定，因此在大地水准面模型中，偏高也作为次要或间接影响进入。与地面重力异常相比，卫星重力任务，特别是GRACE和GOCE得出的重力和大地水准面模型没有这些不一致之处。这些模型可以被认为是无偏的。在回顾了这个问题的数学公式之后，本文探讨了解决这个问题的两种方法。首先比较了GOCE无偏重力场在100 ~ 200度范围内的重力势系数与组合模式EGM2008的重力势系数，该范围受高度偏置的影响。第一个建议产生的解决方案太不准确而无用。第二种方法比较了GNSS椭球高度和偏正态高度的高度异常，以及结合了200度以上的卫星模型和200度以上的高分辨率全球模型的异常势。关键是要表明，在最后一种组合中，高度偏差的间接影响可以忽略不计。为此，进行了误差预算分析。证明了高频部分的偏差是无关的，因此发现每个GNSS站的精度为5 cm。这似乎是解决这个问题的一个很有前途的实用方法。
Regional height systems do not refer to a common equipotential surface, such as the geoid. They are usually referred to the mean sea level at a reference tide gauge. As mean sea level varies (by ±1 to 2 m) from place to place and from continent to continent each tide gauge has an unknown bias with respect to a common reference surface, whose determination is what the height datum problem is concerned with. This paper deals with this problem, in connection to the availability of satellite gravity missions data. Since biased heights enter into the computation of terrestrial gravity anomalies, which in turn are used for geoid determination, the biases enter as secondary or indirect effect also in such a geoid model. In contrast to terrestrial gravity anomalies, gravity and geoid models derived from satellite gravity missions, and in particular GRACE and GOCE, do not suffer from those inconsistencies. Those models can be regarded as unbiased. After a review of the mathematical formulation of the problem, the paper examines two alternative approaches to its solution. The first one compares the gravity potential coefficients in the range of degrees from 100 to 200 of an unbiased gravity field from GOCE with those of the combined model EGM2008, that in this range is affected by the height biases. This first proposal yields a solution too inaccurate to be useful. The second approach compares height anomalies derived from GNSS ellipsoidal heights and biased normal heights, with anomalies derived from an anomalous potential which combines a satellite-only model up to degree 200 and a high-resolution global model above 200. The point is to show that in this last combination the indirect effects of the height biases are negligible. To this aim, an error budget analysis is performed. The biases of the high frequency part are proved to be irrelevant, so that an accuracy of 5 cm per individual GNSS station is found. This seems to be a promising practical method to solve the problem.