On the performance of a low-cost single-frequency GPS+BDS RTK positioning model

When the GPS was the only satellite constellation in orbit, instantaneous single-frequency precise (millimeter-level) positioning was not possible and more expensive survey-grade multiple-frequency receivers had to be used. With the advent of the GNSSs, such as the Chinese BDS, low-cost receiver precise positioning will potentially become feasible. In this contribution we investigate the performance of such a low-cost single-frequency GPS+BDS model, making use of ublox EVK-M8T receivers, and compare its performance to a survey-grade dual-frequency GPS receiver solution, in Dunedin New Zealand. The least-squares variance-component estimation (LS-VCE) procedure is used to investigate the precision of the receiver code and phase observables of the low-cost receivers. The estimated (co)variances are needed so as to formulate a realistic stochastic model for precise RTK positioning. The performance of ambiguity resolution would otherwise deteriorate and hence the achievable positioning precisions as well. The low-cost RTK performance is then evaluated by formal and empirical ambiguity success-rates and positioning precisions. Our results indicate that the quality of the antennas used plays an important role, especially in suppressing multipath. We will demonstrate that the low-cost solution, which costs a few hundred USDs, can give a competitive ambiguity resolution and positioning performance to the survey-grade receivers, which cost several thousand USDs.