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Enhancements to GPS operations and clock evaluations using a "total" Hadamard deviation.
David A Howe1, Ron L Beard, Charles A Greenhall
1Time and Frequency Division, National Institute of Standards and Technology, Boulder, CO 80305, USA. dhowe@boulder.nist.gov
Summary
This study introduces Hadamard-total deviation for improved Global Positioning System (GPS) clock confidence. The new method enhances estimation accuracy, offering a more reliable tool for GPS operations.
Area of Science:
- Navigation and Geodesy
- Signal Processing
- Timekeeping
Background:
- Global Positioning System (GPS) operations rely on accurate timekeeping.
- Hadamard deviation is a key metric for estimating clock stability in GPS.
- Existing methods for Hadamard deviation estimation have limitations in confidence and bias.
Purpose of the Study:
- To introduce a novel method, Hadamard-total deviation, to enhance the confidence of Hadamard deviation estimation.
- To address bias issues in deviation estimation for GPS satellite clocks.
- To improve the management of present and future GPS satellite clocks.
Main Methods:
- Utilizing the total deviation approach to refine Hadamard deviation estimation.
- Implementing a power-law detection scheme for automatic bias removal.
- Analyzing the relationship between Kalman filter parameters and Hadamard/Allan variances.
Main Results:
- Hadamard-total deviation shows a 1.3 to 3.4 times increase in confidence compared to plain Hadamard deviation at longest averaging times.
- The new method introduces a slight negative bias, managed by restricting tau values (<= T/3).
- Automatic bias removal via power-law detection is demonstrated.
Conclusions:
- Hadamard-total deviation offers a significant improvement in confidence for GPS clock stability estimation.
- The proposed method provides a more robust approach to managing GPS satellite clock parameters.
- This advancement is crucial for the reliability of current and future GPS systems.