SBAS Integrity Monitoring via Station Deviation Filtering
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Solution Overview
Problem
Satellite Based Augmentation Systems (SBAS) face limitations in availability and precision due to a limited number of observation stations, and integrating external stations is challenging without compromising integrity checks.
Innovation Solution
A method is introduced to validate the integrity of external radio-navigation stations by calculating deviations in pseudo-distances and excluding stations with significant errors, allowing for case-by-case filtering rather than bulk filtering by satellite or ionosphere zone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If external radio-navigation stations are integrated into the SBAS system to increase the number of observation stations, then the availability and geographical coverage of the service are improved, but the integrity of the system is compromised due to lack of quality control on external station measurements
Solution Approach 1:
The patent applies preliminary action by performing integrity verification of external stations before their measurements are used in the SBAS system. The control and processing center calculates quality indicators for each external station and pre-identifies unreliable stations, excluding them from further processing. This prevents compromised measurements from affecting system integrity while still allowing reliable external stations to contribute to increased availability.
Solution Approach 2:
The patent implements feedback by continuously monitoring the quality of measurements from external stations and using this information to dynamically adjust which stations are trusted. The system calculates quality indicators based on deviations between measured and theoretical pseudo-distances, and this feedback loop enables the system to identify and exclude problematic stations while maintaining contributions from reliable ones, thus resolving the contradiction between using more stations and ensuring their reliability.
2Reliability
If traditional integrity check methods are applied to external stations, then the reliability of measurements is improved, but the availability of the system is reduced due to bulk filtering by satellite or ionosphere zone
Solution Approach 1:
The patent applies segmentation by dividing the integrity verification process into station-level individual assessments rather than bulk filtering. Each external station is evaluated independently based on its own quality indicator calculated from its measurement deviations. This granular approach allows the system to exclude only the specific stations that fail integrity checks while retaining all reliable stations, avoiding the overly conservative bulk filtering by satellite or ionosphere zone that would reduce availability.
3Productivity
If the number of observation stations is increased to improve service coverage, then the availability is improved, but the precision of orbital and ionospheric models deteriorates due to lack of quality control
Solution Approach 1:
The patent applies preliminary action by pre-verifying the quality of each external station before its measurements are incorporated into orbital and ionospheric modeling. The control and processing center calculates quality indicators and excludes unreliable stations in advance, ensuring that only high-quality measurements from verified stations contribute to the models. This maintains measurement precision while still allowing the system to benefit from the increased geographical coverage provided by additional external stations.
Data Source
AI summary
The method involves calculating discrepancies between theoretical pseudo-distances and measured pseudo-distances, for observation stations (RIMS). Average of the discrepancies over a zone is calculated for a satellite (SAT) in vicinity of the zone. Integrity of each observation station of the zone is validated if the discrepancy is less than or equal to the average multiplied by a predetermined exclusion threshold for the station and for a line of sight between the station and the satellite. The station is excluded when the discrepancy is greater than the average. Independent claims are also included for the following: (1) a monitoring and processing center for a satellite based augmentation system (2) a satellite based augmentation system.