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Session A6: GNSS Integrity and Augmentation

Nominal GPS Signal Deformations: 10 years of WAAS Signal Quality Monitoring
R. Eric Phelts, Todd Walter, Stanford University; Rhiannon Sanchez, Federal Aviation Administration; Kristy Pham, William J. Hughes FAA Technical Center
Location: Beacon B

Peer Reviewed

Peer Reviewed

Approximately 10 years of continuous WAAS signal quality monitoring measurements (SQM) have been collected and numerous anomalous signal deformation events have been cataloged over that time. SQM historical data is used to assess the stability and evolution of nominal signal distortions of the L1 C/A code signals from all the GPS satellites in operation over this time period. In addition, the availability of L5 signals data and the addition of GPS Block III SVs allows comparisons to the original L1 monitoring algorithm and predicted monitor performance for the future. Old and new satellites and signals are evaluated, and changes to the system and detection algorithm and their potential effects on past, present, and future performance are assessed. It is shown that the WAAS SQM measurements are quite sensitive to changes in nominal signal deformations. And, while the nominal deformations are quite stable and though significant signal anomalies and faults tend to be rare, unexpected events can and do occur. Andl, even with the addition of GPS III SVs, the maximum nominal range biases on L1 and L5 codes of the current GPS constellation continue to be well-bounded by the minimum range error limits required to guarantee integrity single-frequency WAAS aviation users. It is anticipated this will hold true well into the future for dual frequency WAAS users as well.



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