Feature extraction and suitability analysis of gravity matching navigation reference map

 Objectives:   Gravity matching aided navigation has gradually become a research hotspot in the field of underwater integrated navigation. Its positioning accuracy is closely related to the gravity variation characteristics of the navigation area, so the selection of navigation suitable matching area is very important to ensure the performance of gravity matching aided navigation. In the selection of matching areas for gravity navigation, the previous methods mainly focus on small-scale local simulation data, and the differences in gravity field characteristics between different sea areas are not fully considered. This paper selects high-precision satellite altimetry global ocean gravity field model data to conduct multi-parameter characteristics analysis of gravity navigation reference maps at different scales.   Methods:   In this paper, we select the high-precision satellite altimetry global ocean gravity field model data, and analyze the multi-parameter characteristics of gravity navigation reference maps at different scales for the global sea area, the South China Sea and the Western Pacific Ocean. The global sea area was divided into 23 areas, and the South China Sea and the Western Pacific Ocean into 20 areas. By calculating multiple characteristic parameters of each area, the global sea area large-scale and local sea area gravity matching navigation suitable matching areas were graded. A multi-parameter Marine gravity matching navigation matching area was selected, and the matching navigation simulation was carried out in the South China Sea and the Western Pacific Ocean. Marine gravity matching navigation suitable matching area selection, based on evaluation of local gravity field variation intensity as the core, through comparing different navigation suitable matching area matching navigation test validation, establish local gravity field characteristics in the area and the corresponding relation of gravity matching navigation performance, specific steps are as follows: (1) Gravity matching navigation sea area partition; (2) Calculation of local characteristics and assessment of information richness; (3) Sorting, grading and selection of navigation matching area; (4) Performance verification of matching navigation and positioning.   Results:   The test results show that the higher the level of navigation matching area, the higher the average positioning accuracy of gravity matching navigation in this area. There is a significant correlation and consistency between the gravity matching navigation and positioning accuracy in different areas and the variation trend of local gravity field characteristic parameters. The results of navigation matching area selection of gravity field characteristic parameters have high reliability, and the selected higher level navigation matching area can generally obtain higher accuracy of matching navigation and positioning. Therefore, the partition and selection results of navigation matching areas in this paper can clearly and reliably reflect the matching navigation and positioning effects of different areas, so as to provide an important reference for ocean tests and route planning.   Conclusions:   Improvement and elaboration of Marine/underwater gravity matching navigation reference map, accurate assessment of gravity navigation precision of the reference map, will further improve the veracity and reliability of gravity matching navigation matching area selection, significantly improve the stability and robustness of the underwater gravity matching aided navigation system, and for our passive underwater long-endurance autonomous navigation positioning to provide a more solid technical support.