Acta Geodaetica et Cartographica Sinica ›› 2025, Vol. 54 ›› Issue (8): 1416-1426.doi: 10.11947/j.AGCS.2025.20240361

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An efficient discretization approach for the short-arc integral equation based on Adams and KSG integrators

Shaobin HU1(), Qiujie CHEN1(), Yunzhong SHEN1, Xingfu ZHANG2   

  1. 1.College of Surveying and Geo-Informatics, Tongji University, Shanghai 200092, China
    2.Department of Surveying and Mapping, Guangdong University of Technology, Guangzhou 510006, China
  • Received:2024-09-01 Revised:2025-06-27 Online:2025-09-16 Published:2025-09-16
  • Contact: Qiujie CHEN E-mail:hu08180815@163.com;qiujiechen@tongji.edu.cn
  • About author:HU Shaobin (2001—), male, PhD candidate, majors in time-variable gravity field estimation for gravity satellites. E-mail: hu08180815@163.com
  • Supported by:
    The National Natural Science Foundation of China(42174099);The National Key Research and Development Program of China(2021YFB3900101)

Abstract:

The short-arc integral approach is a widely used technique for satellite-based gravity field recovery, which essentially provides an integral solution to Newton's equation of motion based on the boundary value condition. Considering that Adams and KSG integrators are multistep methods for single and double integrals respectively, this paper proposes a discretization approach for the short-arc integral formula by integrating both Adams and KSG integrators. Consequently, concise formulas have been derived to calculate the coefficients for discretizing the integral equations, thereby contributing to efficient discretization of the short-arc integral equations. Taking the simulation calculation of GRACE-FO satellites as a case study, the proposed approach is compared with the conventional short-arc integral approach from multiple perspectives: computation of discretization coefficients for integral equations, integration of position and velocity vectors, solution of partial derivatives with respect to spherical harmonic coefficients, and gravity field estimation. The results suggest that: ① The discretization coefficient matrices exhibit a high level of consistency between the two approaches, with the RMS (root mean square) of the differences for the position and velocity equations at the orders of 10-9 and 10-6, respectively. However, compared to the conventional approach, the proposed approach significantly enhances efficiency in calculating the discretization coefficient matrices by approximately 80% for position equation and 90% for velocity equation. ② The proposed approach exhibits comparable integration error for velocity vector to the conventional approach using the same arc length, while demonstrating slightly higher accuracy in position vector integration under longer arc lengths. ③ The partial derivatives of the position and velocity equations with respect to spherical harmonic coefficients obtained from both approaches are generally consistent; however, discrepancies arise at high degrees due to low signal energy at those degrees. ④ The accuracy of the resulting gravity field models remains comparable between the two approaches, while the proposed approach significantly enhances the efficiency of solving gravity field models by 74.4% compared with the conventional numerical integral approach.

Key words: short-arc integral approach, Adams, KSG, discretization

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