Code-Carrier Multipath Detection for GNSS Positioning
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Solution Overview
Problem
Multipath errors in global navigation satellite systems (GNSS) lead to measurement inaccuracies, which existing technologies fail to effectively detect and mitigate, affecting positioning accuracy.
Innovation Solution
A method that generates a code-carrier difference for each satellite and signal frequency combination, filters out unknown bias and random noise, and determines the presence of multipath errors, allowing for the exclusion of error-prone measurements from position computations based on trust levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If more satellites are used in GNSS positioning, then positioning availability and coverage are improved, but measurement accuracy deteriorates due to increased multipath errors from additional satellite signals
Solution Approach 1:
The patent extracts and removes multipath-affected satellite measurements from the positioning calculation by detecting multipath errors through code-carrier difference analysis. This selective exclusion of problematic measurements allows the system to maintain high satellite availability while improving positioning accuracy by eliminating error-prone data points.
Solution Approach 2:
The patent applies different quality assessments to different satellite measurements individually. Each satellite signal is evaluated for multipath content, and measurements are weighted or excluded based on their local quality characteristics rather than treating all satellites uniformly. This enables selective use of high-quality measurements while rejecting low-quality ones.
2Adaptability or versatility
If code range measurements are used for positioning, then satellite signal coverage is improved, but measurement reliability deteriorates due to multipath errors affecting code measurements
Solution Approach 1:
The patent introduces code-carrier difference as an intermediary indicator to detect multipath errors. By comparing code range and carrier phase measurements, the system creates a difference metric that reveals multipath contamination. This intermediary allows the system to maintain use of code measurements for coverage while identifying and excluding unreliable measurements through the difference analysis.
3Measurement precision
If multipath detection and exclusion processing is added, then positioning accuracy is improved, but system complexity increases due to additional computational steps
Solution Approach 1:
The patent makes the code-carrier difference calculation serve multiple functions: it simultaneously monitors satellite signal quality, detects multipath errors, and provides input for satellite exclusion decisions. This multi-functionality reduces overall system complexity by consolidating what could be separate processing steps into a single versatile computation.
Solution Approach 2:
The patent changes the processing approach from evaluating raw code and carrier measurements separately to analyzing their difference. This parameter transformation simplifies multipath detection by converting a complex quality assessment problem into a simpler threshold-based decision on the code-carrier difference metric, reducing computational burden while maintaining accuracy.
Data Source
AI summary
A method comprises generating a respective code-carrier difference for each of a plurality of satellite vehicle and signal frequency combinations, wherein the code-carrier difference is based on a code range and a carrier range. The method also comprises filtering the respective code-carrier difference for an unknown bias and random noise; determining whether multipath is present for each of the plurality of satellite vehicle and signal frequency combinations based on the respective filtered code-carrier difference; and computing a position solution based on trust placed in respective measurements from each of the plurality of satellite vehicle and signal frequency combinations, the trust based on whether multipath is present for the respective satellite vehicle and signal frequency combination.