GPS + Galileo Single-Frequency Relative Positioning With Low-Cost Receivers

摘要

During the past decade, Galileo (Europe) and BeiDou (China) satellite systems have been expanded, bringing their total number of in-orbit satellites to 26 and 35, respectively. In combination with GPS (USA), the redundancy of observations has increased, improving the precision, availability and robustness of satellite positioning worldwide. Low-cost single-frequency receivers could largely benefit from these combinations of GNSS, as for instance in the case of safety-of-life applications, for which system failure may be critical. In this contribution, we tested the possibility of improving the positioning performances of single-frequency low-cost receivers by using a tight combination of Galileo E1 + GPS L1 frequency. We evaluated positioning precisions of u-blox EVK M8T receivers, which cost a few hundred USDs, in multi-GNSS relative positioning based on code and phase double differences (DD). We compared the results obtained with those of geodetic receivers, which cost thousands of USDs. The use of a unique-pivot satellite for both constellations in GPS L1 + Galileo E1 double differences introduces differential receiver hardware delays between GPS and Galileo, also called Inter-System Biases (ISBs). We studied both ISBs between low-cost receivers and ISBs between low-cost and geodetic receivers in an ISBs-float short baseline double difference model. We then quantified the positioning precision improvement brought by multi-GNSS single-frequency ISBs-fixed solutions with respect to ISBs-float solutions and multi-GNSS double differences where ISBs are ignored.