Calibration and analysis of BDS receiver-dependent code biases: Fid-Bau Portal

Calibration and analysis of BDS receiver-dependent code biases

Zhang, Yize / Kubo, Nobuaki / Chen, Junping / Wang, Ahao

Abstract Different designs of receiver correlators and front ends will cause different biases in terms of the pseudorange. In this paper, we present an algorithm to derive GNSS receiver-dependent code biases by estimating an additional code bias for each satellite based on different orbit and clock products and apply the calibrated biases in user positioning. One-month data from 117 globally distributed multi-GNSS experiment stations are selected to analyze the characteristics of BeiDou Navigation Satellite System (BDS) code biases, including BDS-2 and BDS-3 satellites. It is shown that the BDS code biases on B1I and B3I signals differ by receiver type, receiver model, antenna type, or even unknown factors. The code biases on BDS-2 satellites can reach up to 4 ns from peak to peak, while they are within 2 ns for BDS-3 satellites. The receiver-dependent code biases are calibrated based on the broadcast ephemeris and the precise products. With a correlation coefficient of approximately 0.9, it is demonstrated that the calibrated code biases are in agreement not only among different products, but also with previous result of BDS-2. To validate the effect of the calibrated code biases, we apply them in single point positioning (SPP), precise point positioning (PPP), and real-time kinematic (RTK) positioning. It is proven that with corrected BDS code biases, SPP users will benefit from an overall improvement of 9.5%, 9.9%, and 27.4% at B1I, B3I, and B1I/B3I ionosphere-free frequencies. For the ionosphere-free based positioning using BDS-3 only, the impact of code biases cannot be ignored. The corrected code biases will accelerate the convergence performance in PPP. For RTK applications, especially for single-frequency users, the fixing rate and ratio values will also improve when the code biases are corrected.