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

Area of Science:

• Geodesy and Geomatics
• Satellite Navigation Systems
• Signal Processing

Background:

• Global Navigation Satellite System (GNSS) observations are crucial for Positioning, Navigation, and Timing (PNT) services but are affected by various errors.
• Multipath (MP) errors in pseudorange observations can be significant (decimeters to meters), yet high-precision correction models are lacking.
• Previous studies confirmed MP-elevation correlations for BDS-2, but BDS-3 multi-frequency MP characteristics require further analysis.

Purpose of the Study:

• To develop and validate a multi-frequency algorithm for extracting pseudorange multipath (MP) errors from BDS-3 observations.
• To analyze the characteristics of MPs across different BDS-3 frequencies and assess the impact of ionospheric delays and noise.
• To investigate the correlation between BDS-3 MPs and satellite elevation angles.

Main Methods:

• A novel multi-frequency MP extraction algorithm based on the least squares principle was developed.
• The algorithm simultaneously eliminates higher-order ionospheric delays, with an analytical expression derived for first-order ionospheric delay elimination.
• Analysis involved extracted MPs from various frequency combinations, assessing combination noise effects, and examining long-term observations from BDS-3 MEO and IGSO satellites.

Main Results:

• The proposed algorithm successfully extracts MPs from BDS-3 observations, considering multi-frequency combinations and ionospheric effects.
• The study details the impact of combination noise on MP extraction accuracy and analyzes the influence of second-order ionospheric delay.
• Periodic behaviors in long-term observations of BDS-3 MEO and IGSO satellites were identified, and quantitative correlations between MPs and satellite elevation were established.

Conclusions:

• The developed multi-frequency MP extraction algorithm offers a more accurate approach for analyzing BDS-3 signal errors.
• Understanding MP characteristics across different frequencies and their correlation with elevation is crucial for improving PNT service reliability.
• This research provides valuable insights for future modeling efforts to mitigate multipath effects in GNSS.