Dual Antenna GNSS Heading Computation with Ambiguity Resolution
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Solution Overview
Problem
Global navigation satellite system (GNSS) signal measurements introduce errors in vehicle positioning and altitude calculations due to ambiguities, particularly when single-frequency GPS measurements are used, leading to low probability of correct fix (PCF) and poor integrity, especially during poor satellite geometries.
Innovation Solution
A method and system using dual antennas with a known baseline length to estimate carrier phase ambiguities, determine integer ambiguities, and compute vehicle heading by linearizing the measurement model, incorporating probability of almost fixed (PAF) values to enhance integrity and accuracy, and applying a hold solution for improved system availability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If single-frequency GPS measurements are used, then device complexity is reduced, but measurement precision and integrity deteriorate due to ambiguities in positioning calculations
Solution Approach 1:
The patent segments the measurement process into multiple components: carrier phase measurements, pseudorange measurements, and ambiguity resolution. By separating these components and processing them independently through dual antennas, the system achieves high precision without requiring complex multi-frequency equipment, thus resolving the contradiction between device complexity and measurement precision.
Solution Approach 2:
The patent introduces carrier phase measurements as an intermediary to bridge the gap between simple single-frequency GPS signals and high-precision positioning requirements. The carrier phase measurements serve as a mediator that provides additional information to resolve ambiguities and improve integrity without requiring complex receiver hardware.
2Measurement precision
If carrier phase measurements are used to improve positioning accuracy, then measurement precision improves, but reliability deteriorates due to integer ambiguities in carrier phase
Solution Approach 1:
The patent implements feedback mechanisms through ambiguity resolution processes that continuously monitor and adjust carrier phase measurements. The system uses feedback from pseudorange measurements and geometric information to correct and validate carrier phase data, ensuring reliability while maintaining high precision through iterative refinement of the positioning solution.
Solution Approach 2:
The patent changes the parameter representation by transforming carrier phase measurements from raw integer ambiguities to resolved float values through measurement linearization. This parameter transformation allows the system to maintain the precision benefits of carrier phase measurements while eliminating the reliability issues associated with integer ambiguities through continuous parameter adjustment and validation.
3Measurement precision
If dual antennas with known baseline length are used, then measurement precision improves for heading determination, but device complexity increases
Solution Approach 1:
The patent makes the dual antenna system universal by using the same baseline length information for multiple purposes: positioning, heading determination, and integrity assessment. The known baseline length serves as a multi-functional reference that enables the system to achieve high precision across different measurement types without requiring separate complex subsystems for each function.
Solution Approach 2:
The patent adds a spatial dimension by introducing a second antenna separated by a known baseline length, transforming single-point positioning into differential measurement capability. This dimensional addition enables heading determination and improves measurement precision through baseline-based geometric relationships without requiring complex signal processing algorithms.
4Reliability
If probability of almost fixed (PAF) values are incorporated to enhance integrity, then reliability improves, but measurement precision may deteriorate due to conservative corrections
Solution Approach 1:
The patent implements dynamic adjustment of integrity thresholds based on PAF values and measurement conditions. The system dynamically adapts the balance between reliability and precision by adjusting correction thresholds in real-time, allowing high precision when confidence is high and conservative corrections when uncertainty increases, thus resolving the contradiction between reliability and measurement precision through dynamic control.
Data Source
AI summary
Systems and methods of heading determination with global navigation satellite system (GNSS) signal measurements are provided herein. A pair of antennas may be separated by a known baseline length and mounted on a vehicle. A GNSS receiver may obtain pseudorange and carrier phase measurements for GNSS satellites within view. An LRU may estimate carrier phase ambiguities and a two-dimensional vector, using the known baseline length and a linearized measurement model. The LRU may determine integer ambiguities using the estimated carrier phase ambiguities. The LRU may determine assumed wrong fixes of the integer ambiguities and a probability of almost fixed value. The LRU may store the set of integer ambiguities. The LRU may determine, from accumulated data over measurement epochs, updated integer ambiguities. The LRU may correct the carrier phase measurements using the updated integer ambiguities. The LRU may compute the heading using the corrected carrier phase measurements.