A Comparative Study of BDS Triple-Frequency Ambiguity Fixing Approaches for RTK Positioning

Area of Science:

• Geodesy and Geomatics
• Satellite Navigation Systems
• Signal Processing

Background:

• Integer ambiguity resolution is critical for high-precision GNSS positioning.
• Triple-frequency systems offer potential for improved performance but require optimized ambiguity resolution strategies.
• Existing approaches include simultaneous fixing, combined ambiguity fixing, and sequential fixing.

Purpose of the Study:

• To comparatively evaluate three distinct triple-frequency ambiguity resolution strategies.
• To develop a consistent processing framework for direct comparison of different fixing approaches.
• To assess the impact of sequential versus integrated fixing on positioning performance.

Main Methods:

• Developed a processing strategy to generate consistent normal equations for all three fixing approaches.
• Implemented simultaneous fixing of original ambiguities, fixing of combined ambiguities (EWL, WL), and sequential fixing (EWL, WL, B1).
• Conducted experimental validation using four baselines (static and kinematic) and analyzed metrics like Time to First Fixed Solution (TFFS), fixing rate, accuracy, and RATIO.

Main Results:

• Sequential fixing of extra-wide-lane (EWL), wide-lane (WL), and B1 ambiguities outperformed integrated searching methods.
• Simultaneous fixing of original ambiguities and fixing of combined ambiguities showed comparable performance.
• Utilizing third-frequency data significantly reduced TFFS but offered minimal improvement in positioning accuracy.

Conclusions:

• Sequential ambiguity fixing strategy provides superior performance for triple-frequency GNSS.
• Integrated fixing approaches yield similar results, while sequential fixing enhances precision.
• The primary benefit of triple-frequency systems lies in accelerated ambiguity resolution, not enhanced positioning accuracy.