Geolocation Accuracy via Erroneous Satellite Measurement Filtering
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Solution Overview
Problem
GPS geolocation determination is often inaccurate due to 'multipath' effects and receiver clock drift, leading to erroneous satellite measurements.
Innovation Solution
A method and apparatus that determine an approximate location of a receiver, calculate range differences between expected and measured satellite ranges, calculate a median value, and compare offset values with a threshold to detect and filter out erroneous satellite measurements, using only accurate measurements for location determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If GPS signals are received from multiple satellites for position determination, then location coverage and availability are improved, but measurement accuracy deteriorates due to multipath effects and clock drift causing erroneous satellite measurements
Solution Approach 1:
The patent extracts and removes erroneous satellite measurements from the set of all received satellite signals. By identifying measurements that deviate significantly from the median range difference and excluding them from position calculation, the system eliminates the harmful effect of multipath and clock drift errors while maintaining the benefit of using multiple satellite signals for location determination.
Solution Approach 2:
The patent implements a feedback mechanism where the calculated position is used to compute expected range differences, which are then compared with measured range differences to identify erroneous measurements. This closed-loop feedback process continuously refines the selection of valid satellite measurements, improving position accuracy while maintaining adaptability to different satellite geometries and signal conditions.
2Productivity
If all received satellite signals are used for position calculation, then processing speed is improved, but position accuracy deteriorates due to inclusion of erroneous measurements from multipath effects
Solution Approach 1:
The patent performs preliminary identification and flagging of erroneous satellite measurements before they are used in position calculation. By pre-processing the satellite signals to detect and mark problematic measurements based on range difference analysis, the system avoids the need for complex real-time error correction during position computation, thus maintaining processing speed while improving accuracy.
3Measurement precision
If threshold for erroneous measurement detection is lowered to improve accuracy, then position precision is improved, but reliability deteriorates due to potential false rejection of valid satellite measurements
Solution Approach 1:
The patent dynamically adjusts the threshold parameter for erroneous measurement detection based on the statistical distribution of range differences from multiple satellites. By setting the threshold at a multiple of the median absolute deviation rather than using a fixed value, the system adapts to different signal conditions and satellite geometries, maintaining high precision while avoiding false rejection of valid measurements under varying operational conditions.
Data Source
AI summary
The disclosure relates to method and apparatus for geolocation determination. In one embodiment, the disclosure relates to a method for detecting an erroneous satellite measurement by a receiver, including the steps of (a) determining an approximate location of the receiver; (b) for each of a plurality of satellites from which the receiver receives a signal: (i) determining a range difference between an expected range between the receiver and the satellite and a measured range between the receiver and the satellite; (ii) determining a median value of the range differences; (iii) determining an offset value between the range difference and the median value; (iv) comparing the offset value with a predetermined threshold to thereby detect an erroneous satellite measurement.