Satellite Positioning Integrity via Virtual Beacon Path Comparison
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Solution Overview
Problem
Current integrity-checking algorithms for satellite-based position determination systems, such as GNSS RTK, SBAS, and RAIM, are inadequate for critical safety applications like the railway sector, as they require multiple visible satellites and are sensitive to masking/multi-path/interference effects, failing to provide adequate protection levels, especially with stringent requirements like 4 meters of protection and a risk of loss of integrity of 10^-10.
Innovation Solution
A method that uses a satellite receiver and a database of virtual beacons to estimate the delay between received and theoretical geopositioning signals, comparing the estimated heading with stored path segment headings to identify unreliable positions, and sets a protection level based on the probability of path misdetection to ensure accurate and reliable positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional integrity-checking algorithms (GNSS RTK, SBAS, RAIM) are used, then the system can operate with standard satellite visibility requirements, but the protection level is insufficient for critical safety applications requiring 4 meters accuracy with 10^-10 risk of loss of integrity
Solution Approach 1:
The patent introduces virtual beacons as intermediary reference points distributed along predefined paths. These virtual beacons serve as mediators between the satellite receiver and the actual position determination, enabling integrity checking by comparing estimated positions against known beacon locations and path geometries. This intermediary system allows the use of fewer satellites while maintaining high reliability through geometric constraints and hypothesis testing.
Solution Approach 2:
The patent segments the continuous path into discrete path segments with associated virtual beacons. By dividing the positioning space into segments and testing hypotheses about which segment the receiver occupies, the system achieves high precision integrity checking without requiring multiple satellites. Each segment hypothesis can be evaluated independently using geometric relationships between the receiver, virtual beacons, and satellites.
2Measurement precision
If multiple satellites are required for position determination, then the system achieves better geometric dilution of precision, but the system becomes sensitive to masking, multi-path, and interference effects
Solution Approach 1:
The patent changes the fundamental parameter from satellite count to path geometry constraints. Instead of relying on multiple satellites for geometric diversity, the system uses the known geometry of predefined paths and virtual beacon locations as constraints. This parameter change allows position determination with fewer satellites while maintaining precision through geometric validation against the known path structure, reducing sensitivity to satellite masking and interference.
3Device complexity
If the system uses statistical protection levels based on signal-to-noise ratio, then the computation is simpler, but the integrity cannot be guaranteed when the absolute positioning error exceeds the alert level
Solution Approach 1:
The patent performs preliminary action by pre-defining paths, placing virtual beacons at known locations, and establishing path segment hypotheses before position determination occurs. This preliminary setup creates a framework of geometric constraints that can be quickly validated during operation. The system pre-computes expected signal characteristics and geometric relationships, enabling simple real-time integrity checking that guarantees reliability by validating positions against the pre-established path geometry rather than relying on statistical estimates.
Data Source
AI summary
A method for checking an estimated location of a mobile machine receiving geopositioning signals from satellites, k=1 to s; a database storing the geographical coordinates of virtual beacons and the heading of the path segment on which the virtual beacon is located; a location indicating a virtual beacon, estimated to be on the same path segment as the machine, wherein for k=1 to s: the delay, ΔτS<sub2>k</sub2>(t,B1), is computed between the geopositioning signal received from and the theoretical geopositioning signal; values hdg and RxB1 are estimated that respect:ΔτS1(t,B1)=1c(cos(el1))-1cos(az1′)RxB1+ε1⋮ΔτSs(t,B1)=1c(cos(els))-1cos(azs′)RxB1+εsthe location being identified as unreliable depending on comparison of the estimated hdg with the stored value of the heading of the path segment of the beacon.