Correction Model of BDS-3 Satellite Pseudorange Multipath Delays and Its Impact on Single-Frequency Precise Point Positioning

Abstract

Precise point positioning (PPP) is used in many fields. However, pseudorange multipath delay is an important error that restricts its accuracy. Pseudorange multipath delay can be considered as the combination of effective information and observation noise; it can be modeled after removing the observation noise. In this work, elastic nets (EN) regularization denoising method is proposed and compared with L2-norm regularization denoising method. Then, quadratic polynomial (QP) model plus autoregressive (AR) model (QP + AR) are used to model the denoised pseudorange multipath delays. Finally, the modeling results are corrected to the observations to verify the improvement of BDS-3 single-frequency PPP accuracy. Three single-frequency PPP schemes are designed to verify the effectiveness of denoising method and QP + AR model. The experimental results show that the accuracy improvement of B3I and B2a is more obvious than that of B1I and B1C when the modeling values are corrected to the pseudorange observations. The improvement of B3I and B2a in the east (E) and up (U) directions can reach 10.6%∼34.4% and 5.9%∼65.7%, and the improvement of the north (N) direction is mostly less than 10.0%. The accuracy of B1I and B1C in E and U directions can be improved by 0%∼30.7% and 0.4%∼28.6%, respectively, while the accuracy of N direction can be improved slightly or even decreased. Using EN regularization denoising and QP + AR model correction, single-frequency PPP performs better at B3I and B2a, while L2-norm regularization denoising and QP + AR model correction perform better at B1I and B1C. The accuracy improvement of B2a and B3I is more obvious than that of B1I and B1C. The convergence time after MP correction of each frequency is slightly shorter. Overall, the proposed pseudorange multipath delays processing strategy is beneficial in improving the single-frequency PPP of BDS-3 satellite.

Research on Linear Combination Models of BDS Multi-Frequency Observations and Their Characteristics

“…PMP can be extracted by using the combination of pseudorange and carrier-phase observations. The PMP of a satellite on frequencies i and j can be written as [33,48]:…”

“…Similar to Equation (31), MP 1 contains PMP 1 , ambiguity term, hardware delay bias, and other biases. If no cycle slip occurs within a period, PMP 1 can be obtained by [48]:…”

“…Multipath delay is one of the main error sources in the GNSS measurement. The multipath delay impact of pseudorange can reach the meter-level, while the carrier-phase is at most 1/4 cycle, much smaller than that of pseudorange [6,48]. The PMP is mainly extracted by the DF combination of pseudorange and carrier-phase observations.…”

The Extraction and Characterization of Pseudorange Multipath Based on BDS-3 Multi-Frequency Observations

“…Compared with other navigation systems, the BDS satellite constellation is composed of three types of orbiting satellites: geostationary orbit (GEO), IGSO, and MEO. Both the IGSO and MEO satellites of BDS-3 can transmit observations of five frequency signals [3,4]. Despite the increased complexity in process-ing the observations of multi-orbit and multi-frequency signals, this ability significantly improves the overall service performance and accuracy of the system [5,6].…”