GNSS Multipath Mitigation via Satellite Exclusion
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Solution Overview
Problem
Current Global Navigation Satellite Systems (GNSS) receivers struggle to accurately determine position and velocity due to multipath errors, which are not effectively addressed by existing technologies, especially in scenarios where satellites' signals are orthogonal to the vehicle's motion, leading to persistent and difficult-to-handle biases.
Innovation Solution
The method involves using a GNSS receiver that determines an approximate vehicle velocity vector and calculates a dot product between the line of sight to each satellite and the vehicle's velocity vector, removing satellite measurements below a minimum dot product threshold to eliminate multipath errors and improve position solution accuracy, with the option to adjust the threshold based on geometric reliability factors to include more measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If satellite measurements are selectively removed based on dot product threshold to eliminate multipath errors, then position and velocity solution accuracy is improved, but the number of available satellite measurements is reduced
Solution Approach 1:
The patent extracts and removes satellite measurements that are likely to contain multipath errors by calculating the dot product between the line-of-sight vector to each satellite and the vehicle velocity vector. Measurements with dot products below a minimum threshold are excluded from the position solution calculation, thereby eliminating the harmful multipath components while retaining valid measurements.
Solution Approach 2:
The patent changes the parameter used to evaluate satellite measurement quality from traditional geometric dilution of precision (GDOP) metrics to a velocity-based dot product criterion. By using the dot product between line-of-sight and velocity vectors, the system identifies and removes measurements where the satellite signal is orthogonal to the vehicle motion, which are most susceptible to multipath errors.
2Measurement precision
If a strict minimum dot product threshold is applied to remove multipath errors, then measurement accuracy is improved, but the geometric reliability factor may deteriorate due to fewer measurements
Solution Approach 1:
The patent implements a dynamic threshold adjustment mechanism where the minimum dot product threshold is not fixed but adapts based on the geometric reliability factor. When the geometric reliability deteriorates due to removal of too many measurements, the threshold is relaxed to include more measurements, thereby maintaining a balance between multipath error elimination and geometric reliability.
Solution Approach 2:
The system employs feedback by continuously monitoring the geometric reliability factor after removing measurements based on the dot product threshold. If the geometric reliability falls below an acceptable level, the system adjusts the threshold parameter and re-evaluates the measurement set, creating a closed-loop control that balances error elimination with solution reliability.
Data Source
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AI summary
A method of operating a global positioning receiver is provided. The method includes receiving a plurality of signals from a plurality of satellites. At least a measurement from and location of each satellite is determined based on the received plurality of signals. An approximate vehicle velocity vector is determined based on the received plurality of signals. A dot product between a line of sight between each satellite and a vehicle having the receiver and the determined vehicle velocity vector is determined. Each measurement associated with each determined dot product that is below a minimum dot product threshold is removed to obtain a resultant set of measurements. A position solution based on the resultant set of measurements is then determined.