Ambiguity resolution (AR) is crucial for high-precision indoor pseudolite positioning. Due to the existing characteristics of the pseudolite positioning system, such as the geometry structure of the stationary pseudolite which is consistently invariant, the indoor signal is easy to interrupt and the first order linear truncation error cannot be ignored, and a new AR method based on the idea of the ambiguity function method (AFM) is proposed in this paper. The proposed method is a single-epoch and nonlinear method that is especially well-suited for indoor pseudolite positioning. Considering the very low computational efficiency of conventional AFM, we adopt an improved particle swarm optimization (IPSO) algorithm to search for the best solution in the coordinate domain, and variances of a least squares adjustment is conducted to ensure the reliability of the solving ambiguity. Several experiments, including static and kinematic tests, are conducted to verify the validity of the proposed AR method. Numerical results show that the IPSO significantly improved the computational efficiency of AFM and has a more elaborate search ability compared to the conventional grid searching method. For the indoor pseudolite system, which had an initial approximate coordinate precision better than 0.2 m, the AFM exhibited good performances in both static and kinematic tests. With the corrected ambiguity gained from our proposed method, indoor pseudolite positioning can achieve centimeter-level precision using a low-cost single-frequency software receiver.

Purpose: Global positioning system (GPS) kinematic positioning suffers from performance degradation in constrained environments such as urban canyons, which then restricts the application of high-precision vehicle positioning and navigation within the city. In December 2012, the BeiDou Navigation Satellite System (BDS) regional service was announced, and the combined BDS/GPS kinematic positioning has been enabled in the Asia-Pacific area. Previous studies have mainly focused on the performance evaluations of combined BDS/GPS static positioning. Not much work has been performed for kinematic vehicle positioning under constrained observation conditions. This study aims to analyze the performance of BDS/GPS kinematic vehicle positioning in various conditions. Design/methodology/approach: In this study, three vehicle experiments under three observation conditions, an open suburban area, a less dense non-central urban area and a dense central urban area, are investigated using both the code-based differential global navigation satellite system (DGNSS) and phase-based real-time kinematic (RTK) modes. The comparison between combined BDS/GPS and GPS-only vehicle positioning solutions is conducted in terms of positioning availability and positioning precision. Findings: Numerical results show that the combined BDS/GPS system significantly outperforms the GPS-only system under poor observation conditions, whereas the improvement was less significant under good observation conditions. Originality/value: Thus, this paper studies the performance of combined BDS/GPS kinematic relative positioning under various observation conditions.