Abstract
Global Navigation Satellite System (GNSS) is an important technical tool for building deformation monitoring, but in complex environments such as urban canyons, the GNSS signals received by monitoring stations are susceptible to severe multipath errors, resulting in a significant decrease in positioning precision. The multipath hemispherical map (MHM) model is a common method to mitigate multipath errors in GNSS, but its performance can be compromised by high-frequency multipath errors, outliers, and non-line-of-sight signals caused by nearby obstructions. In this study, an MHM model with geographic cut-off elevation constraints is proposed, which considers signal quality and terrain topography surrounding the station to mask those unsatisfactory signals, and leverages the advantages of the MHM model for mitigating low-frequency multipath. To validate the effectiveness of the proposed method, a GNSS deformation monitoring experiment was carried out in an urban environment. The results show that the root mean square (RMS) values of horizontal and vertical positioning errors for the ambiguity-fixed solution using the proposed method are 0.40 and 0.68 cm, respectively, showing improvements of 65.9% and 63.4% compared to the solution without multipath correction (M0), 43.8% and 37.0% to the solution using traditional MHM model (M1), and 63.2% and 50.0% to the solution using geographic cut-off elevation model (M2), respectively. Correspondingly, the ambiguity fixing rate increased from 84.95%, 95.31% and 98.97% of M0, M1 and M2 solutions to 99.95%. The proposed MHM model with geographic cut-off elevation constraints can improve the positioning precision, and thus would be helpful for GNSS deformation monitoring in complex environments.
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Data availability
The datasets used and analyzed during the current study are available from the corresponding author on reasonable request.
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Acknowledgements
Thanks to the RTKLIB open source program package for providing the method validation platform. We thank all the editors and anonymous reviewers for their valuable, constructive and prompt comments.
Funding
This work is funded by the StateKey Research and Development Programme (No. 2021YFC3000504), the National Natural Science Foundation of China (No. 42204021), the Hubei Luojia Laboratory (220100021), the Fundamental Research Funds for the Central Universities (No. 2042022kf1035), the China Postdoctoral Science Foundation (No. 2022M722443).
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GL conceived the project and the main conceptual ideas. GL and HR worked out almost all of the technical details and performed the numerical calculations for the suggested experiments; PL and HR conducted the experiments; FW provided the fisheye camera image and processed the sky map data; HR, GL and JG wrote the paper.
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Ren, H., Li, G., Geng, J. et al. Multipath hemispherical map model with geographic cut-off elevation constraints for real-time GNSS monitoring in complex environments. GPS Solut 27, 188 (2023). https://doi.org/10.1007/s10291-023-01530-5
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DOI: https://doi.org/10.1007/s10291-023-01530-5