## 4 Application Scenarios of the Multipath Error Mitigation Algorithm
### GNSS Deformation Monitoring
With the development of global satellite navigation and positioning technology, multi-GNSS system data fusion processing has become a future development trend [93]. This evolution is expected to enhance the usability and reliability of GNSS deformation monitoring [94]. At present, GNSS monitoring technology has been widely used in monitoring fields such as high-rise buildings, dams, bridges, and building tailings. In terms of water dams, in 1995, [PERSON] and Hudnut [95] developed the first GNSS dam non-real-time deformation monitoring system to monitor the deformation displacement of the Pacoima dam by continuously operating the GPS monitoring station system. The GNSS monitoring system can measure the horizontal and vertical displacements of water dams and surrounding adjacent areas, and can obtain centimeter-level or even millimeter-level deformation information [96]; it has also gradually become an important component of the dam safety and stability monitoring system [97]. High-rise buildings and large bridge structures are easily deformed or even damaged by external factors, such as wind, earthquakes, temperature, and vehicles [98]. [PERSON] et al. [99] established SmartSync, a rapidly deployable health and safety monitoring system at the Burj Khalifa, which accommodates multiple sensor types, including GPS, accelerometers, and weather stations, to monitor real-time deformation information of the Burj Khalifa in Dubai in order to ensure the structural health and safety of the entire structure. [PERSON] et al. [100] applied GPS to the British Humber Bridge for monitoring experiments. The analysis of the verification test results showed that the GPS signal measurement results obtained very good experimental data, which is consistent with the finite element model analysis results. In terms of landslide monitoring, GNSS monitoring technology performs static calculations through satellite observation data over a period of time and obtains deformation and displacement information of landslide monitoring points within a corresponding period of time. [PERSON] et al. [101] analyzed the reliability and accuracy of GPS technology applied to the dynamic real-time deformation monitoring of landslides by using large-scale physical model tests of landslides. Obtaining accurate deformation information of the monitored object is the primary purpose of deformation monitoring. The existence of multipath errors seriously affects the data quality of monitoring points and reduces the availability of monitoring point positioning results [102]. When the error is serious, it causes the wrong deformation disaster warning of the monitored object [103]. [PERSON] et al. [104] corrected the multipath error of the GPS data of the Foss Road Bridge through the single-difference sidereal filtering method, and the results showed that the positioning accuracy of the bridge deformation monitoring was greatly improved compared with the original results. [PERSON] et al. [105] used the sidereal filtering method to correct the multipath errors of GNSS landslide deformation monitoring data in the Qinba mountainous area and loess monitoring environment in real time, and the positioning residual accuracy was improved to the millimeter level. [PERSON] et al. [106] considered that tropospheric errors and multipath errors exist simultaneously in long-baseline real-time kinematic (RTK) positioning, and corrected tropospheric errors and multipath errors successively by using the undifferenced residuals of satellites. This research provided an effective research strategy for long-baseline, high-precision, real-time dynamic carrier-phase difference technology RTK deformation monitoring. [PERSON] et al. [107] used non-difference, single-difference, and double-difference sidereal filtering methods to process high-speed railway-based BeiDou satellite monitoring data, and the positioningaccuracy in the three directions was effectively improved.