Comparison of Three Methods for Estimating GPS Multipath Repeat Time

Minghua Wang,Jiexian Wang,Wen Chen,Ling Han,Haojun Li,Danan Dong

doi:10.3390/rs10020006

Abstract

Sidereal filtering is an effective method for mitigating multipath error in static GPS positioning. Using accurate estimates of multipath repeat time (MRT) in sidereal filtering can further improve the performance of the filter. There are three commonly used methods for estimating the MRT: Orbit Repeat Time Method (ORTM), Aspect Repeat Time Adjustment (ARTA), and Residual Correlation Method (RCM). This study utilizes advanced sidereal filtering (ASF) adopting the MRT estimates derived by the three methods to mitigate the multipath in observation domain, then evaluates the three methods in term of multipath reduction in both coordinate and observation domain. Normally, the differences between the MRT estimates from the three methods are less than 1.2 s on average. The three methods are basically identical in multipath reduction, with RCM being slightly better than the other two methods, whereas for a satellite affected by orbit maneuver (satellite number 13 in this study), the MRT estimated by the three methods differ by up to tens of seconds, and the RCM- and ARTA-derived MRT estimates are better than ORTM-derived ones for ASF multipath reduction. The RCM shows a slight advantage in multipath mitigation, while ORTM is the one of lowest computation and ARTA is the optimal one for real-time ASF. Thus, the best MRT estimation method for practical applications depends on which criterion overweighs the others.

Highlights

For a GPS station, the multipath effects depend on the surroundings of the specific site and the geometric relationship between the GPS receiver and satellites [1,2]
We compared the multipath repeat time (MRT) estimates derived by Orbit Repeat Time Method (ORTM), Aspect Repeat Time Adjustment (ARTA), and Residual Correlation Method (RCM), and compared the multipath mitigating effectiveness of advanced sidereal filtering (ASF) adopting the MRT estimates from the three methods
Our results show that the average of the differences between MRT estimates derived by ORTM and ARTA is less than one second, which is consistent with the results of Fang [10] and

Summary

Introduction

For a GPS station, the multipath effects depend on the surroundings of the specific site and the geometric relationship between the GPS receiver (antenna) and satellites [1,2]. It is still a challenge to develop a general multipath correction model for different GPS stations. Assuming that the surrounding conditions related to this site are constant every day, the multipath effects for this site appear to be repeated at a sidereal day as well. Based on this time-domain repeatability, Bock et al [3,4] proposed a method named sidereal filtering to mitigate multipath error for static GPS positioning. The general principle of sidereal filtering is the construction of a multipath correction model from the residuals of coordinates or observables of the previous day(s), the correction of the data of the subsequent day(s) by subtracting the corresponding correction value for each epoch

Methods

Results

Discussion

Conclusion