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Uncertainty Quantification of First Fix in a Time-Differenced Carrier Phase Observation Model
Hakim Cherfi1, Julien Lesouple1, Joan Solà2
1Fédération ENAC ISAE-SUPAERO ONERA, Université de Toulouse, 7, Avenue Edouard Belin, 31400 Toulouse, France.
Initial position errors in Global Navigation Satellite System (GNSS) odometry significantly impact displacement estimation. This study quantifies these errors in time-differenced carrier phase (TDCP) models, showing a linear relationship between initial position error and displacement error.
Area of Science:
- Geomatics Engineering
- Satellite Navigation Systems
- Signal Processing
Background:
- Time-differenced carrier phase (TDCP) is crucial for precise Global Navigation Satellite System (GNSS) odometry.
- Accurate initial position is a critical assumption in TDCP modeling, often unmet in real-world scenarios.
Purpose of the Study:
- To perform uncertainty quantification of the first fix in TDCP observation models.
- To assess the impact of initial position errors on GNSS-based displacement estimation.
Main Methods:
- Formulated correct and misspecified TDCP models to analyze initial position error effects.
- Derived theoretical frameworks for estimation under misspecified models, including Mean Squared Error (MSE) and Misspecified Cramer-Rao Bound (MCRB).
- Conducted extensive simulations with realistic GNSS geometry to evaluate performance under varying conditions.
Main Results:
- Displacement estimation error is linearly related to the initial position error and the time interval between observations.
- Demonstrated that a 10m initial first-fix error in a 1s TDCP can introduce up to 1.3mm displacement error.
- Quantified the order of magnitude of errors introduced by parameter uncertainties in GNSS solutions.
Conclusions:
- Accurate first-fix estimation is vital for reliable TDCP-based odometry.
- The study provides a quantitative understanding of how initial position uncertainties propagate through TDCP models.
- Findings are essential for improving the robustness and accuracy of GNSS displacement estimation techniques.
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