Multi-GNSS Combined Orbit and Clock Solutions at iGMAS.

Area of Science:

• Geodesy and Geomatics Engineering
• Satellite Navigation Systems
• Space Geodesy

Background:

• Global Navigation Satellite Systems (GNSS) like GPS, GLONASS, BDS, and Galileo are operational.
• The international GNSS monitoring and assessment system (iGMAS) provides a unified framework for evaluating these systems.
• Accurate orbit and clock products are essential for assessing user range error (URE) and overall navigation performance.

Purpose of the Study:

• To describe the combination method for iGMAS orbit and clock products from multiple analysis centers.
• To evaluate the performance and reliability of these combined GNSS products.
• To assess the impact of orbit and clock errors on positioning accuracy using combined solutions.

Main Methods:

• Combined orbit and clock products from multiple analysis centers within the iGMAS framework.
• Validation using Satellite Laser Ranging (SLR) observations for orbit accuracy assessment.
• Precise Point Positioning (PPP) and simulated kinematic tests to validate consistency and positioning accuracy.

Main Results:

• Combined orbit and clock solutions demonstrate enhanced robustness and reliability compared to single analysis center solutions.
• Root-mean-square error (RMSE) of 5 cm achieved for BDS-3, Galileo, and GLONASS combined orbits using SLR.
• Centimeter-level accuracies (1.4 cm East, 1.2 cm North, 2.9 cm Up) obtained in simulated kinematic tests using PPP.

Conclusions:

• The iGMAS combination method yields high-precision orbit and clock products for the quad-constellation GNSS.
• Identified solar radiation pressure (SRP) model deficiencies necessitate further improvements in precise orbit determination.
• The combined products are suitable for high-accuracy applications, including precise point positioning and kinematic positioning.