ARAIM Availability Prediction Using Terrain Shielding Angles
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Solution Overview
Problem
Existing ARAIM availability prediction methods fail to consider the influence of terrain barriers, leading to inaccuracies in predicting satellite visibility and protection levels, which are crucial for ensuring flight safety in complex environments like near mountains or airports in valleys.
Innovation Solution
An ARAIM availability prediction method that calculates terrain shielding angles using digital elevation model data to determine visible satellites, predicts fault modes, and calculates protection levels, thereby improving prediction accuracy by considering terrain influences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional ARAIM availability prediction methods are used without considering terrain barriers, then the prediction process is simple, but the prediction accuracy of satellite visibility and protection levels deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-calculating terrain shielding angles based on digital elevation model data before performing ARAIM availability prediction. This pre-computed terrain information is then integrated into the satellite visibility determination process, allowing the system to account for terrain barriers without adding complexity during the actual prediction execution.
Solution Approach 2:
The patent introduces terrain shielding angles as an intermediary parameter that mediates between the complex terrain environment and the satellite visibility determination. By using this intermediate metric derived from digital elevation models, the system can indirectly account for terrain effects without directly modeling complex terrain-satellite-receiver interactions.
2Reliability
If terrain barriers are not considered in satellite visibility prediction, then the calculation process is fast, but the reliability of ARAIM availability prediction deteriorates in complex terrain environments
Solution Approach 1:
The patent performs preliminary calculation of terrain shielding angles from digital elevation model data before the main prediction process. This pre-computation stores terrain obstruction information in advance, allowing the prediction algorithm to quickly query pre-calculated shielding angles rather than performing complex terrain analysis during real-time prediction, thus maintaining both reliability and productivity.
3Measurement precision
If terrain shielding angles are calculated using digital elevation model data, then the accuracy of visible satellite prediction improves, but the computational complexity increases
Solution Approach 1:
The patent uses terrain shielding angles as an intermediary representation of terrain effects. Instead of performing complex ray-tracing or line-of-sight analysis between satellites and receivers considering detailed terrain features, the system pre-calculates shielding angles from digital elevation models and uses these angles to filter visible satellites, significantly reducing computational complexity while maintaining prediction accuracy.
Data Source
AI summary
An ARAIM availability prediction method under a complex terrain environment is provided. The method includes: 1) selecting positioning points according to an air line; 2) calculating terrain shielding angles; 3) predicting visible satellites; 4) determining a fault mode that needs to be monitored; 5) calculating a positioning error variance, an influence coefficient of a nominal deviation, and a variance of a solution separation test statistic; and 6) calculating a threshold of a solution separation test, calculating a protection level, and determining availability. According to the method, the terrain shielding angles are calculated based on terrain model data, and the visible satellites are predicted based on ephemeris data or almanac data to further calculate a protection level, while determining the availability; and the accuracy of availability prediction can, by considering the effect of terrain barriers on the prediction of the visible satellites, be improved to ensure the safety of aircrafts.