GPS Engine Type Detection via UERE Hysteresis Filtering
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Solution Overview
Problem
The varying assumptions of GPS engines regarding satellite errors result in different Horizontal Figure of Merit (HFOM) values, necessitating the detection of GPS engine type to ensure optimal operation, especially with the deactivation of Selective Availability (SA), which affects GPS accuracy and compatibility across different systems.
Innovation Solution
A method utilizing HFOM and Horizontal Dilution of Precision (HDOP) values to compute User Equivalent Range Error (UERE), filtered through a hysteresis process, to determine the GPS receiver type, allowing for appropriate threshold adjustments based on the engine type.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the SA-on GPS engine is used, then the GPS accuracy is degraded to 55-100 meters, but the system maintains compatibility with older SA-on assumptions
Solution Approach 1:
The system dynamically adjusts HFOM threshold values based on the detected GPS engine type. The threshold is set to 100 meters for SA-on engines and 18 meters for SA-off engines, allowing the system to adapt its acceptance criteria to match the capabilities of different GPS engines while maintaining operational compatibility
Solution Approach 2:
The invention changes the HFOM parameter threshold based on the detected engine type. By detecting whether the GPS receiver uses SA-on or SA-off engine and adjusting the HFOM threshold accordingly, the system optimizes position acceptance criteria to match the actual accuracy capabilities of each engine type
2Measurement precision
If the SA-on/off GPS engine is used, then the GPS accuracy improves to 18-46 meters, but the system complexity increases due to multiple engine types
Solution Approach 1:
The system performs self-detection of the GPS engine type by analyzing the relationship between HFOM and HDOP values. The detector automatically identifies whether the receiver uses SA-on or SA-off engine and configures appropriate thresholds without requiring manual intervention or complex configuration procedures
Solution Approach 2:
The system uses feedback from the GPS receiver's reported HFOM and HDOP values to automatically detect the engine type and adjust the HFOM threshold accordingly. This closed-loop approach simplifies system operation by allowing the detector to self-configure based on the actual performance characteristics of the connected GPS receiver
3Measurement precision
If the Dynamic SA-on/off GPS engine is used, then the GPS accuracy is optimized to 10-18 meters, but the difficulty of detecting and measuring engine type increases
Solution Approach 1:
The invention replaces complex engine identification mechanisms with a mathematical analysis approach. By analyzing the relationship between HFOM and HDOP values through computation and filtering, the system detects engine type based on performance characteristics rather than requiring direct identification of the engine model or configuration
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate detection of GPS engine type, optimizing system performance by setting appropriate HFOM limits, thereby enhancing GPS accuracy and compatibility, particularly in environments where SA is deactivated.
Implementation Method 1
The filtered UERE value is run through a hysteresis to determine the GPS receiver type
Data Source
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AI summary
An apparatus and method for detecting the type of Selective Availability (SA) engine in a Global Positioning System (GPS) receiver. The apparatus (30) reverse computes a User Equivalent Range Error (UERE) value and filters it. The filtered value is run through a hysteresis to determine the GPS engine type. The engine type determination is used to adjust values used by other systems.