GNSS Measurement Filtering for RTK and PPP Accuracy
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Solution Overview
Problem
Precise positioning techniques like RTK and PPP are affected by GNSS measurements subject to multipath and other challenging conditions, leading to degraded measurement quality and reduced positioning accuracy.
Innovation Solution
The method involves receiving GNSS correction data and determining the standard deviation of pre-fit residuals for various GNSS measurement types. Based on these calculations, conditional triggers are set to modify how the positioning engine processes the measurements, potentially excluding or de-weighting certain measurements to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If all GNSS measurements are processed without filtering, then the quantity of measurements used for positioning is maximized, but the accuracy of position estimates degrades due to multipath and challenging conditions
Solution Approach 1:
The patent applies preliminary action by performing quality assessment of GNSS measurements before they are used in positioning calculations. The system evaluates pre-fit residuals and signal characteristics in advance to identify and filter poor-quality measurements, ensuring only reliable data enters the positioning engine. This prevents degradation of position accuracy while maintaining processing efficiency.
Solution Approach 2:
The patent extracts and removes harmful elements from the measurement set by identifying measurements with excessive pre-fit residuals or poor signal characteristics. These problematic measurements are excluded from the positioning solution, thereby eliminating their negative impact on accuracy while preserving the beneficial measurements.
2Measurement precision
If strict filtering criteria are applied to exclude poor-quality measurements, then the accuracy of position estimates improves, but the quantity of usable measurements decreases
Solution Approach 1:
The patent dynamically adjusts filtering parameters based on the observed quality of incoming measurements. Rather than applying fixed strict criteria, the system modifies thresholds and weights according to pre-fit residual analysis and signal characteristics, optimizing the balance between accuracy and measurement quantity in real-time.
Solution Approach 2:
The filtering process is made dynamic by continuously evaluating measurement quality metrics and adapting the acceptance criteria accordingly. The system can relax or tighten filtering based on current environmental conditions and measurement reliability, ensuring optimal use of available data without compromising accuracy.
3Reliability
If adaptive measurement filtering is implemented to handle multipath conditions, then the robustness of positioning solutions improves, but the computational load and processing time increase
Solution Approach 1:
The patent performs quality assessment calculations before the main positioning computation, evaluating pre-fit residuals and signal metrics in advance. This preliminary filtering prepares clean measurement data for the positioning engine, improving robustness against multipath without adding significant delay during critical positioning operations.
Data Source
AI summary
A global navigation satellite system (GNSS) device may receive GNSS correction data and may determine a respective standard deviation of pre-fit residuals of one or more GNSS measurement types of a set of GNSS measurements. The GNSS device may determine at least one conditional trigger is met based on a comparison of the respective standard deviation of pre-fit residuals of the one or more GNSS measurement types with a respective threshold, and, responsive to determining the at least one conditional trigger is met, may modify how a positioning engine processes one or more measurements of the set of GNSS measurements. The GNSS device may determine a position estimate of the GNSS device based at least in part on a result of the modified processing of the one or more measurements by the positioning engine and the GNSS correction data.