GPS Ground Speed Validation for RAAS False Advisory Prevention
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Solution Overview
Problem
False 'On Taxiway' advisories are produced due to erroneous Global Positioning System (GPS) ground speed data, especially when the aircraft is not moving, leading to incorrect conflict awareness alerts in Runway Awareness and Advisory Systems (RAAS).
Innovation Solution
A system that determines the reliability of GPS ground speed by comparing changes in GPS track information and ground speed, setting the GPS ground speed to zero if unreliable, and sending this validated or unreliable data to RAAS to prevent false advisories, utilizing a processor that receives data from GPS, Inertial Reference System, and other aircraft systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GPS ground speed data is used directly by RAAS, then the system can provide conflict awareness advisories, but false 'On Taxiway' advisories are produced when GPS ground speed is erroneous
Solution Approach 1:
The system performs preliminary validation of GPS ground speed data by comparing it with inertial reference system data before the data is used by RAAS. This advance checking prevents erroneous data from triggering false advisories, thereby improving reliability without compromising the advisory function.
Solution Approach 2:
The system introduces an intermediary validation process that mediates between the GPS receiver and RAAS. This intermediary compares GPS ground speed with inertial reference data and only passes validated data to RAAS, eliminating false advisories while maintaining the conflict awareness function.
2Measurement precision
If GPS ground speed is monitored continuously, then accurate speed data can be provided to RAAS, but system complexity increases
Solution Approach 1:
The validation system uses the aircraft's existing inertial reference system to validate GPS data. The inertial system already provides acceleration and position data as part of its normal operation, so the validation process leverages this existing capability without requiring separate validation hardware, thereby maintaining measurement precision while limiting complexity increase.
Solution Approach 2:
The system merges the GPS validation function with the existing inertial reference system. By combining these two data sources and using the inertial system to validate GPS ground speed, the system achieves accurate speed monitoring while avoiding the complexity of a completely separate validation system.
Data Source
AI summary
Methods and systems for determining reliability of Global Positioning System (GPS) ground speed. An example system receives GPS track information and GPS ground speed, determines a change in GPS track information and determines reliability of the GPS ground speed based on the determined change in GPS track information relative to the GPS ground speed. The system sets a GPS ground speed based on the determined reliability. A GPS ground speed output is set to zero, if the GPS ground speed is determined unreliable and the GPS ground speed output is set to the GPS ground speed, if the GPS ground speed is determined reliable. The system sends the GPS ground speed output to a Runway Awareness and Advisory System (RAAS). Also, the system sets the GPS ground speed output to zero, if a received GPS ground speed validity signal or a received GPS track validity signal indicate invalid.