GNSS Position Velocity Uncertainty Metrics
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Solution Overview
Problem
Conventional GPS systems inaccurately determine position and velocity due to invalid assumptions about measurement noise variance, particularly in urban environments where satellite signals are attenuated or multipath affected, leading to unequal variances and time-varying biases.
Innovation Solution
A system and method that calculates separate independent estimates of pseudorange and delta range measurement noise variances for each satellite signal, accounting for multipath effects and using these estimates within a Kalman filter-based approach to improve position and velocity determinations, incorporating dynamic process noise estimates based on user dynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional GPS systems use standard measurement noise variance assumptions, then the system remains simple and computationally efficient, but position and velocity determination accuracy deteriorates in urban environments with multipath effects and signal attenuation
Solution Approach 1:
The patent changes the measurement noise variance parameter from a fixed uniform value to satellite-specific time-varying values. Each satellite's pseudorange and delta range measurements are assigned individual noise variance estimates that adapt to changing signal conditions, thereby improving measurement precision without requiring fundamental system redesign
Solution Approach 2:
The patent segments the measurement noise modeling by separating pseudorange noise variance from delta range noise variance, and further segmenting each by satellite source. This allows independent estimation and optimization of noise characteristics for each measurement type and satellite, improving overall position and velocity accuracy while maintaining manageable computational complexity through modular processing
2Reliability
If GPS receivers assume equal measurement noise variance for all satellites, then computational processing remains efficient, but measurement reliability deteriorates when some satellites experience multipath or attenuation
Solution Approach 1:
The patent performs preliminary estimation of measurement noise variances before the main position calculation process. By pre-computing satellite-specific noise variance values for pseudorange and delta range measurements, the system prepares accurate weighting factors in advance, ensuring reliable measurement selection without adding computational burden during the critical position solution phase
Solution Approach 2:
The system implements feedback by using the estimated measurement noise variances to weight measurements in the Kalman filter or least squares solution. Measurements with lower estimated noise variance receive higher weights, automatically improving reliability by emphasizing more trustworthy satellite signals while maintaining computational efficiency through standard estimation algorithms
3Measurement precision
If the system models measurement noise realistically with satellite-specific variances, then position and velocity accuracy improves in challenging environments, but computational complexity increases
Solution Approach 1:
The patent implements self-service by having the GPS receiver automatically estimate its own measurement noise variances from the received satellite signals. The system uses the observed signal characteristics and measurement residuals to compute satellite-specific noise variance values without requiring external calibration or complex manual configuration, thereby improving accuracy while keeping the system self-contained and computationally manageable
Data Source
AI summary
A GNSS navigation system and navigation method for determining user position, user velocity, and improved uncertainty metrics for position and velocity. A measurement engine in an applications processor of the system determines pseudorange and delta range values over each time period for each received satellite signal, and also determines measurement noise variances for both pseudorange and delta range for the individual signals. The satellite-specific pseudorange and delta range measurement variances are used to determine the position and velocity uncertainties by a position engine, either by way of a least-squares linearization or by way of an enhanced Kalman filter. The uncertainties may be communicated to the system user, or used in generating an integrated position and velocity result from both the GNSS navigation function and an inertial navigation system result.