Prefilter Lock Detection for Reliable Ultratight GPS Measurements
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Solution Overview
Problem
Existing navigation systems do not ensure the most accurate and reliable epoch timing information is extracted and validated for computing navigation solutions, particularly in ultratight GPS and INS coupling, leading to potential inaccuracies in position and velocity data.
Innovation Solution
A navigation system utilizing multiple prefilters operating in parallel with observation lock detectors and a measurement selector to provide a measurement error vector and lock indicator and confidence vector, ensuring the most reliable measurement errors are used for robust navigation solutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple prefilters are used in parallel to extract epoch timing information, then the reliability and accuracy of measurement errors improve, but the device complexity increases
Solution Approach 1:
The patent divides the signal processing into multiple parallel prefilters (first prefilter, second prefilter, third prefilter), each handling different aspects of epoch timing information extraction. This segmentation allows independent optimization of each prefilter while maintaining overall system reliability through redundancy and comparison of results.
Solution Approach 2:
The patent employs different filtering parameters and thresholds for each prefilter based on signal conditions. The observation lock detector adjusts processing parameters dynamically based on the quality of epoch timing information extracted by each prefilter, optimizing the balance between accuracy and complexity under varying operational conditions.
2Measurement precision
If observation lock detectors are used to validate measurement errors, then the accuracy of navigation solution improves, but the processing time increases
Solution Approach 1:
The observation lock detector performs preliminary validation of measurement errors from multiple prefilters before they are used in navigation solution computation. By pre-validating the quality and reliability of epoch timing information, the system avoids processing invalid or inaccurate data, thereby improving overall measurement precision while managing processing time through early rejection of poor-quality measurements.
Solution Approach 2:
The observation lock detector provides feedback about the quality of epoch timing information extracted by each prefilter. This feedback mechanism allows the navigation processor to selectively use only the most reliable measurement errors, improving accuracy without requiring all measurements to undergo full processing, thus managing computational time efficiently.
3Reliability
If multiple prefilters process different discriminators, then the robustness in noisy conditions improves, but the difficulty of detecting and measuring accurate epoch timing increases
Solution Approach 1:
The patent segments the epoch timing extraction process into multiple parallel prefilters, each processing different discriminators (carrier phase, carrier frequency, code). This segmentation allows each prefilter to specialize in extracting epoch timing information from specific signal components, making the overall system more robust to noise while distributing the measurement difficulty across multiple independent processing paths.
Solution Approach 2:
The patent adjusts the processing parameters and thresholds of each prefilter based on the specific discriminator being processed and current signal conditions. This parameter adaptation enables accurate epoch timing extraction from different signal representations, reducing the difficulty of measurement while maintaining robustness across varying noise conditions and signal qualities.
Data Source
AI summary
An observation lock detector block receives I&Q correlations and generates error measurement vectors, each including phase, frequency, code, pseudorange, and covariance residual estimates, and generates validity indicator and confidence indicator vectors, one of which error measurement vectors is an output as a selected error measurement vector with a respective validity indicator and confidence indicator vector, both of which selected vectors are communicated to a navigation solution processor in a ultratightly coupled navigation system for providing improved estimations of a navigation solution, the indicators indicating the usefulness of measurement errors, the prefilter detector block comprising discriminators, sequential filters, observation lock detectors and a measurement selector for selecting measurement vector based on phase, frequency, and code discriminations, the measurement errors being residual estimates that are indicated as valid or invalid for dynamic propagation of the residuals in a navigation receiver for improved performance, especially in low signal-to-noise environments, such as, for use in an ultratight GPS navigation system.