Multi-GNSS-Weighted Interpolated Tropospheric Delay to Improve Long-Baseline RTK Positioning

Area of Science:

• Geodesy and Geomatics Engineering
• Atmospheric Science
• Satellite Navigation

Background:

• Real-time kinematic (RTK) and Network-based RTK (NRTK) offer cm-level positioning using GNSS.
• Tropospheric delay, influenced by atmospheric humidity, is a significant error source in RTK, particularly for longer baselines.
• Quantifying tropospheric delay is challenging due to its variability.

Purpose of the Study:

• To estimate double-differenced zenith tropospheric delays (ZTDs) using the NRTK approach.
• To assess the impact of incorporating a priori interpolated ZTDs on positioning accuracy and Integer Ambiguity Resolution (IAR).
• To compare a novel simple interpolation strategy with standard RTK methods.

Main Methods:

• Utilized a 6-station European network with multi-GNSS data for NRTK processing.
• Estimated ZTDs, ambiguities, and positions simultaneously.
• Employed weighted least-squares (WLS) with a priori interpolated ZTDs from nearby IGS network stations, using a simple interpolation strategy to mitigate altitude variability.

Main Results:

• Validated estimated ZTDs against IGS data, achieving an average Root Mean Squares Error (RMSE) of approximately 12 mm.
• Incorporating interpolated ZTDs improved positioning accuracy by about 50% compared to standard RTK.
• The success rate for Integer Ambiguity Resolution (IAR) increased by nearly 1%.

Conclusions:

• The NRTK approach effectively estimates ZTDs, contributing to improved positioning accuracy.
• Using a priori interpolated ZTDs as quasi-observations enhances both positioning precision and IAR performance.
• The proposed simple interpolation strategy offers a practical method to leverage ZTD information in NRTK, outperforming standard RTK.