On High-Frequency Topography-Implied Gravity Signals for a Height System Unification Using GOCE-Based Global Geopotential Models
On High-Frequency Topography-Implied Gravity Signals for a Height System Unification Using GOCE-Based Global Geopotential Models
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DOI：
10.1007/s10712-016-9400-4
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发表时间：
2017-03
影响因子：
4.6
通讯作者：
T. Grombein;K. Seitz;B. Heck
中科院分区：
文献类型：
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作者：
T. Grombein;K. Seitz;B. Heck
国家高度参考系统通常与当地平均海平面相联系，在各个验潮站观察到。由于海面地形的变化，这些系统的基准面不一致，导致高度基准面偏移高达±1-2 m。为了统一高度系统，提出了一种基于卫星的方法，该方法利用来自欧空局卫星使命重力场和稳态海洋环流探测器（GOCE）的全球地球重力位模型（GGM）。在这种情况下，通过将GGM信息与测量的GNSS/水准测量数据进行比较，在最小二乘平差内估计高度基准偏移。虽然GNSS/水准测量数据包括全光谱信息，但GOCE GGM根据其球谐表示的最大程度而限于长波长。为了提供精确的高度基准偏移，必须考虑到高于该最大度数的剩余信号，即GGM的遗漏误差。因此，进行GOCE信息与高分辨率地球引力模型2008（EGM 2008）的组合。本文的主要贡献是分析了额外使用高频地形隐含重力信号来减少EGM 2008剩余遗漏误差的好处。在频谱扩展方面，提出了一种新的方法，不依赖于假定的频谱一致性的地形高度和隐含的重力是残留地形建模（RTM）技术的情况下。在这种新方法的第一步中，重力正演模拟的基础上的镶嵌体质量体根据岩石-水-冰（RWI）的方法。在第二步骤中，通过地形重力场模型RWI_TOPO_2015的影响来减小所得到的基于全光谱RWI的地形势值，从而去除长波长至中波长。通过使用最新的GOCE GGM，地形隐含的重力信号对估计的高度基准偏移的影响进行了详细分析，代表性的GNSS/水准数据集在德国，奥地利和巴西。除了高达3 cm的估计偏移量发生了相当大的变化外，所进行的分析表明，在降低标准差和最小二乘调整残差范围方面，可以实现30-40%的显著改善。
National height reference systems have conventionally been linked to the local mean sea level, observed at individual tide gauges. Due to variations in the sea surface topography, the reference levels of these systems are inconsistent, causing height datum offsets of up to ±1–2 m. For the unification of height systems, a satellite-based method is presented that utilizes global geopotential models (GGMs) derived from ESA’s satellite mission Gravity field and steady-state Ocean Circulation Explorer (GOCE). In this context, height datum offsets are estimated within a least squares adjustment by comparing the GGM information with measured GNSS/leveling data. While the GNSS/leveling data comprises the full spectral information, GOCE GGMs are restricted to long wavelengths according to the maximum degree of their spherical harmonic representation. To provide accurate height datum offsets, it is indispensable to account for the remaining signal above this maximum degree, known as the omission error of the GGM. Therefore, a combination of the GOCE information with the high-resolution Earth Gravitational Model 2008 (EGM2008) is performed. The main contribution of this paper is to analyze the benefit, when high-frequency topography-implied gravity signals are additionally used to reduce the remaining omission error of EGM2008. In terms of a spectral extension, a new method is proposed that does not rely on an assumed spectral consistency of topographic heights and implied gravity as is the case for the residual terrain modeling (RTM) technique. In the first step of this new approach, gravity forward modeling based on tesseroid mass bodies is performed according to the Rock–Water–Ice (RWI) approach. In a second step, the resulting full spectral RWI-based topographic potential values are reduced by the effect of the topographic gravity field model RWI_TOPO_2015, thus, removing the long to medium wavelengths. By using the latest GOCE GGMs, the impact of topography-implied gravity signals on the estimation of height datum offsets is analyzed in detail for representative GNSS/leveling data sets in Germany, Austria, and Brazil. Besides considerable changes in the estimated offset of up to 3 cm, the conducted analyses show that significant improvements of 30–40% can be achieved in terms of a reduced standard deviation and range of the least squares adjusted residuals.