Abstract:

Aiming at the problem of data redundancy in the high latitude region in the construction of gravity field model based on traditional geographic grid data subdivision, this paper introduces the hierarchical equal area isolatitude pixelation (HEALPix) grid structure into the calculation of the Earth's gravity field for the first time, and proposes the construction theory of ultra-high-degree Earth's gravity field model using icosahedral HEALPix (ico_HEALPix) grid. The efficient construction of the global 3600-degree spherical harmonic coefficient is realized, which solves the problems of uneven distribution of traditional geographic grid points and redundancy of high-latitude data. At the same time, the normal matrix of the ico_HEALPix grid is not a strict block diagonalization structure in the process of spherical harmonic analysis. An iterative algorithm is designed to effectively improve the accuracy of model construction. Experiments show that the accuracy of the global Earth gravity field model constructed by the iterative method can be better than that of the geographic grid under the premise that the data volume of the ico_HEALPix grid data is less than about 5 million of the geographic grid, and the error order RMS of spherical harmonic coefficient is increased by 1~2 orders of magnitude. It also solves the problems of north and south pole distortion and data redundancy of the geographic grid, and improves the data utilization of the grid.

Key words: HEALPix grid, ico_HEALPix grid, ultra-high-degree Earth gravity field model, iterative algorithm, least squares method, XGM2019e