Multipath mitigation methods for challenging environments caused by snowy weather in BDS/GPS deformation monitoring

Snowy weather makes the multipath effects of receivers in BDS/GPS short baseline applications more complex. Traditional multipath hemispherical map (MHM) relies on stable observation environments, while the multipath period of the BDS MEO constellation is as long as seven days. Random walk multipath (RWM) utilizes multipath-corrected GPS observations to estimate multipath errors of other systems, providing advantages in challenging environments. We evaluated the performance of MHM and RWM in the BDS/GPS combined system, and the results showed that only the RWM meets the application requirements. Moreover, adopting multi-period modeling data may lead to a decrease in positioning accuracy. Further experiments showed that GPS satellites exhibited higher multipath correlation coefficients than BDS satellites. Considering the limited modeling data, three different RWM schemes are designed and evaluated. Positioning results from two consecutive weeks at Jurong Power Station indicate that the scheme of using GPS to assist all BDS satellites (RWM-G) is more recommended. This was further validated with a week’s data from another reservoir. In addition, a detailed evaluation of RWM-G revealed significant suppression of low-frequency multipath and some suppression but limited of high-frequency ones, with an average residual reduction rate of about 45 % for all satellites. During the initial snowfall period with better observation environments, the improvement of daily solutions in the vertical direction is more significant. In the snow accumulation stage with poor observation environments, the RWM-G can correct positioning offsets, ensuring accurate and reliable results.