基于严密大气和地形归算的区域大地水准面精化研究

Centimeter-level geoid refinement is one of the main scientific objectives of geodesy. The theoretical fundamentals of precise geoid determination is the theory of boundary value problems, in which one of the key issues is how to precisely estimate the effects of the atmospheric and topographic reductions on the geoid. The theoretical model and computation method of traditional atmospheric and topographic reductions are not rigorous, and hence they are not satisfied by the requirement of computing a geoid with a centimeter-level accuracy. In this research, the rigorous atmospheric and topographic reduction method that is well suited for centimeter-level geoid refinement will be studied, the main contents are as follows: the development of a gravity forward modeling algorithm, which can efficiently and accurately compute gravity effects due to a large amount of tesseroids or spherical mass layer elements at an arbitrary point; the determination of rigorous scheme for the shifting of atmospheric masses, which is based on the concept of mass condensation, as well as the construction of an accurate physical model for computing atmospheric effects, which takes a high-resolution digital terrain model and a global quasi-static three-dimensional atmospheric density model into account; the optimal selection of the condensation layer of Helmert’s method of condensation in the case of different topography types, as well as the establishment of a precise physical model for calculating the harmonic corrections in the residual terrain model. Finally, a software system for computing regional geoid models is developed. On the basis of this software system, geoid models in three typical regions are computed by using real gravity data, and the contribution of precise processing of atmospheric and topographic effects to the geoid is quantified. The achievements of this research can provide theoretical and technical support for the refinement of centimeter-level regional geoid and the modernization of national height datum.

厘米级大地水准面精化是大地测量学的主要科学目标之一。确定精密大地水准面的理论和方法基础是大地测量边值问题理论，关键问题之一是如何精确计算大气和地形归算对大地水准面的影响。传统大气和地形归算的理论模型和计算方法存在近似性，已不能满足厘米级精度的要求。本项目拟研究适合厘米级大地水准面精化的严密大气和地形归算理论方法，主要内容包括：开发可快速精确计算空间任意一点由大量球棱柱体或球面质量层产生的重力影响的正演算法；制定严密大气质量调整方案以及构建精密大气影响计算模型；研究不同地形条件下赫尔默特凝集法中凝集层位置的优选策略以及建立残差地形模型法中调和改正的严密计算模型。基于以上成果研制区域大地水准面计算软件系统，利用实测重力数据解算3个典型区域的大地水准面模型，量化精确处理大气和地形影响对大地水准面的贡献。预期成果可为我国厘米级区域大地水准面精化以及国家高程基准现代化提供理论和技术支持。

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