Method for Establishing the Multipath Adaptive Mitigation Model Considering Deformation Displacement of Monitoring Stations

Multipath effects are a significant error source affecting the Global Navigation Satellite System (GNSS) positioning, and their impact cannot be overlooked in millimeter-level positioning applications such as deformation monitoring. Existing methods for multipath mitigation almost universally assume that a GNSS antenna does not undergo displacement. However, in deformation monitoring, the frequent displacements of monitoring points render these methods inapplicable. Therefore, it is imperative to study multipath modeling and mitigation in scenarios where monitoring points are displaced. To address this issue, this study introduces a multipath adaptive mitigation model (MAMM) that investigates the impact of monitoring point displacement on the effectiveness of multipath mitigation in different areas of the hemisphere model. It uses the multipath mitigation values of the normal grid as a constraint to re-estimate the real-time multipath mitigation values for abnormal grid areas, and to design experiments for validation. This study demonstrates that under centimeter-level antenna displacement conditions, the conventional multipath hemisphere model (MHM) shows a significant decrease in positioning accuracy improvement. The areas of abnormal multipath effect variation comprise no more than 20% of the total space, providing theoretical feasibility for the modeling process of this study. Comparisons of positioning accuracy show that, under a 10 mm displacement, the MHM improves positioning accuracy in the east, north, and elevation by 86.4%, 127.2%, and 131.8%, respectively, compared to the original positioning accuracy, whereas the MAMM achieves 115.8%, 162.5%, and 139.1%, respectively, which is comparable to the accuracy of MHM under non-displacement conditions. Under displacements exceeding 50 mm, the MHM's accuracy improvements were 48.1%, 71.1%, and 59.8%, respectively, whereas the MAMM showed 100%, 124.1%, and 107.5%, respectively, significantly outperforming the MHM. Considering that the deformation rates of existing displacement monitoring bodies are generally lower than 10 mm/day, the MAMM demonstrates its effectiveness in reducing multipath errors without the need for repeated modeling, thereby proving its substantial practical value.