3D Attitude Determination Using GNSS Carrier Phase Integrity
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Solution Overview
Problem
Existing navigation systems face challenges in accurately determining 3D angular orientation, particularly heading, due to limitations in magnetometer calibration and GNSS carrier phase noise, especially near magnetic poles and in environments with rapidly changing magnetic fields.
Innovation Solution
A 3D attitude determination system using multiple GNSS antennas and processors to resolve integer ambiguities in carrier phase measurements, employing least-square-error solutions, instantaneous and interval tests, and solution separation functions to ensure integrity and accuracy of heading calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetometer is used to determine heading, then heading can be computed using magnetic field measurements, but heading errors exceed requirements due to calibration limitations and magnetic disturbances
Solution Approach 1:
The patent introduces GNSS carrier phase measurements as an intermediary to determine baseline vectors between antennas, which then serve as a reference for computing heading. This mediator bypasses the magnetic field disturbances that directly affect magnetometer-based heading, allowing the system to achieve accurate and reliable heading determination even in environments with rapidly changing magnetic fields or near magnetic poles
Solution Approach 2:
The patent replaces the magnetometer-based magnetic field measurement system with a GNSS carrier phase-based geometric measurement system. By substituting the mechanical/magnetic sensing approach with an optical/electromagnetic signal processing approach, the system eliminates sensitivity to magnetic disturbances while maintaining heading computation capability
2Adaptability or versatility
If GNSS carrier phase measurements are used to determine heading, then heading is globally available including near magnetic poles, but integrity of integer ambiguity resolution must be assured in the presence of carrier phase noise and multipath noise
Solution Approach 1:
The patent implements feedback mechanisms where the computed baseline vectors from integer ambiguity resolution are continuously validated against expected geometric relationships and measurement residuals. This feedback loop allows the system to detect and correct errors in integer ambiguity resolution, maintaining high integrity even in the presence of carrier phase noise and multipath effects
Solution Approach 2:
The patent performs preliminary validation of carrier phase measurements and pre-processing of data to identify and mitigate potential sources of error before integer ambiguity resolution is attempted. This preliminary action reduces the impact of noise and multipath effects, improving the reliability of subsequent ambiguity resolution
3Ease of operation
If magnetometer calibration is performed, then heading can be computed, but calibration can't keep up with rapidly changing local magnetic fields
Solution Approach 1:
The patent replaces the calibration-based magnetic field measurement system with a GNSS carrier phase-based geometric measurement system. This substitution eliminates the need for calibration that must keep up with changing magnetic fields, as the GNSS-based system derives heading from geometric relationships that are inherently stable and do not require calibration
4Ease of operation
If Earth's magnetic field is used for heading determination, then heading can be computed from magnetic field direction, but magnetic heading is unavailable for flights close to magnetic poles
Solution Approach 1:
The patent introduces GNSS carrier phase measurements as an intermediary that enables heading determination through geometric relationships between antennas and satellites. This mediator provides a alternative heading computation method that does not depend on magnetic field direction, thereby maintaining operational availability near magnetic poles while preserving the simplicity of automated heading computation
Data Source
AI summary
A method of determining three-dimensional attitude is provided. The method includes measuring a carrier phase of each satellite signal received at plurality of spaced antenna. A carrier phase difference between the measured carrier phase for each satellite signal from each satellite received at each antenna is determined. The integrity of the integer ambiguity resolution relating to the carrier phase difference is assured by applying a least-square-error solution using differential carrier phase measurements with applied integer ambiguities between at least two of the plurality of antennas and observing measurement residuals after the least-square-error solution is computed and applying an instantaneous test, an interval test and a solution separation function. Three-dimensional attitude is determined from the carrier phase differences upon completion of the integer ambiguity resolution and the assurance of integrity of the integer ambiguity resolution.