Analysis of the adaptation area for gravity field component matching navigation: A case study in the South China Sea

Gravity field matching navigation achieves high positioning accuracy only within the adaptation region, and thus determining the adaptation region is crucial for the success of gravity field matching navigation. The gravity field consists of multiple components, reflecting variation of the gravity field signals from distinct perspectives. Consequently, the adaptation regions of different gravity field components are, in theory, different. To investigate the differences, this study adopts principal component analysis and a weighted average normalization method, combined with maximum interclass variance method, to comprehensively evaluate four gravity field characteristic parameters. The study derives and analyzes the differences in the matching regions among vertical deflections, gravity anomaly, and full tensor of gravity gradients, while also investigating the underlying causes of these variations. The results show that the matching areas of distinct gravity field components are indeed different; and the matching areas of the gravity gradients are all larger than that of the gravity anomaly. Among gravity gradients, $ {T}_{xy} $ has the largest matching region in the study area, followed by $ {T}_{xz} $; the matching area of $ \xi $ exceeds that of $ \eta $. Furthermore, correlation analysis with respect to water depth reveals that the matching area primarily concentrates in regions characterized by significant changes in terrain. Notably, within the same range of water depth, the matching capabilities of various gravity field components differ. Additionally, this study reveals that maximizing the utilization of each gravity field component enhances the extent of the adaptation area.