Detection of RINEX-2 Files With Mixed GPS L2P(Y)/L2C Carrier Phase Observations

Area of Science:

• Geodesy and Geomatics Engineering
• Satellite Navigation Systems

Background:

• The Global Positioning System (GPS) constellation comprises older and newer satellites.
• Newer GPS satellites (IIR-M, IIF) transmit the L2C signal, while older ones (IIA, IIR) broadcast the legacy L2P(Y) signal.
• The RINEX-2 data format is not designed to simultaneously store carrier phase observations from both L2 signals.

Purpose of the Study:

• To develop and present algorithms for detecting defective RINEX-2 files.
• To identify files containing mixed and unaligned L2P(Y) and L2C carrier phase observations.
• To assess the impact of such defective files on precise positioning.

Main Methods:

• Analysis of widelane fractional ambiguities.
• Application of detection algorithms to RINEX-2 files from 2624 reference stations.

Main Results:

• Seventy-two (2.7%) of the analyzed RINEX-2 files were found to be defective.
• Defective files contained mixed and unaligned L2P(Y) and L2C carrier phase observations.
• Unaligned L2 observations can lead to centimeter-level coordinate errors in long baselines and prevent ambiguity fixing in short baselines.

Conclusions:

• The presence of mixed and unaligned L2 signals in RINEX-2 files poses a significant threat to precise GPS positioning.
• Algorithms based on widelane fractional ambiguities are effective in detecting these defective files.
• Correct data handling is crucial for maintaining the accuracy of GPS-derived coordinates, especially for applications requiring high precision.