Abstract
The multipath effect on carrier-phase observations is related to the observational environment of the station, and cannot be eliminated or attenuated by the differential method. In the actual dam environment of deformation monitoring, multipath is very complicated. It is the main error source of BDS-2 for high precision data processing. In this paper, a new method called the multi-point hemispherical grid model (MHGM) is studied and evaluated. This method uses the hemispheric grid model to attenuate the influence of multipath errors. The effectiveness and improvement of the new method with respect to the popular sidereal filter (SF) method were assessed and verified by the actual dam monitoring data with only the BDS-2. The MHGM and SF approach calculates the multipath corrections from multi-days historical data, and then corrects the multipath error from the observations on the day of interest. Compared with the SF method, the MHGM can also effectively provide a graphical display of multipath error interference around the stations, which matches the surrounding observation environment. The results show that the double-differenced (DD) residuals of the MHGM for GEO/IGSO and MEO satellites are slightly better than those of SF, but the RMS of MHGM for GEO/IGSO+MEO DD residuals is improved by about 17.0%. The performance of the MHGM method for different satellite constellations is consistent and not affected by the different orbital repeat times, which could solve the “zero mean” assumption problem of the SF method. Meanwhile, the RMS of static with a 2 h interval and kinematic positioning errors of the MHGM method in the horizontal and vertical direction can be up to 1.7, 3.6 and 2.4, 8.1 mm, respectively. The MHGM model could avoid the multipath reference problem caused by different orbital repetition periods, making it more suitable for the combined multipath modeling of BDS-2 and BDS-3.
Highlights
Multipath is a major error source that affects the accuracy and reliability of GNSS data processing
In order to assess the performance of the multi-point hemispherical grid model (MHGM), BDS-2 data collected as a part of the deformation monitoring of reservoir were processed
We analyzed and assessed the MHGM method for the mitigation of multipath error at stations based on a multi-point hemispherical grid model
Summary
Multipath is a major error source that affects the accuracy and reliability of GNSS data processing. Multipath error is defined as the total impact of the direct and the reflected signal of GNSS satellite arriving at the receiving antenna, which is usually caused by diffuse and specular reflection. The diffuse multipath generated by the reflection signal on the rough surface is not related with time and has behavior similar to noise [1,2]. Specular multipath from a smooth reflecting surface can cause system errors, for which the maximum value for the carrier phase can be as high as 1/4 wavelength [3]. Many studies have shown that multipath can be mixed into other parameters, such as position, tropospheric parameters and float ambiguity.
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