ARAIM Navigation System Terrain Database Error Handling
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Solution Overview
Problem
Global Navigation Satellite Systems (GNSS) lack sufficient integrity for stringent operations like aircraft landing procedures, necessitating the integration with other sensors to enhance navigation system performance, particularly due to the connection of horizontal and vertical errors in terrain database-induced errors.
Innovation Solution
A navigation system that incorporates a radar altimeter and a terrain database to compute vertical position protection levels by selecting points based on a horizontal protection level, using solution separation methodologies to determine integrity and account for errors, and applying weighted error samples to calculate accurate altitude measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GNSS measurements are merged with radar altimeter and terrain database measurements to improve navigation performance, then measurement accuracy is improved, but terrain database induced errors affect vertical position integrity
Solution Approach 1:
The patent segments the error sources by separating horizontal error analysis from vertical error analysis. It identifies that terrain database errors affect vertical position independently from horizontal position errors, and processes them through separate integrity monitoring channels. This segmentation allows the system to address vertical integrity specifically without being overwhelmed by coupled horizontal-vertical error propagation.
Solution Approach 2:
The patent introduces an intermediary integrity monitoring process that acts between the raw measurements and the final navigation solution. This intermediary layer computes protection levels specifically for vertical position by analyzing terrain database errors separately, then combines these with horizontal integrity information to produce the final vertical position integrity assessment.
2Reliability
If solution separation methodologies are used to determine integrity, then reliability is improved, but device complexity increases
Solution Approach 1:
The solution separation methodology is segmented into distinct computational stages: horizontal integrity computation, vertical error analysis, protection level calculation, and final combination. Each stage processes specific data independently, which simplifies the overall complexity by breaking down the monolithic integrity monitoring task into manageable, specialized sub-tasks.
Solution Approach 2:
Different parts of the integrity monitoring system are assigned different levels of computational complexity appropriate to their function. The horizontal integrity monitoring uses standard GNSS methods, while the vertical integrity monitoring uses specialized terrain database error analysis. This local differentiation of quality and complexity allows the system to achieve high reliability without uniformly increasing complexity throughout the entire system.
Data Source
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AI summary
Systems and methods for handling ARAIM terrain database induced errors are described herein. In certain embodiments, a method includes computing position information from a global navigation satellite system. The method further includes computing altitude based on retrieved information from a vertical position sensor (119) and a terrain database (109). Additionally, the method includes computing a horizontal protection level associated with the position information. Also, the method includes estimating an error for a terrain database based on the altitude, position information, and the horizontal protection level. Moreover, the method includes calculating a new protection level based on the position information and the altitude accounting for the estimated error for the terrain database.