GNSS Rover Positioning via Single-Differenced Delta Phase Processing
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Solution Overview
Problem
Current GNSS technologies face challenges in achieving fast convergence to a solution, improved accuracy, and greater availability, particularly in determining the position of a moving rover relative to a base location, especially at high update rates and with limited computing power, due to issues with carrier-phase ambiguity fixing and accumulation of errors in delta phase position estimates.
Innovation Solution
The method involves using single-differenced delta phase processing to compute changes in the moving-base-rover vector at high rates, combining first-epoch positions with updates to obtain subsequent-epoch positions, and employing weighted averages of carrier-phase ambiguity candidates to converge to a predetermined threshold, allowing for high-update rate GNSS positioning without incorrect ambiguity fixing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If carrier-phase ambiguities are fixed to determine rover position, then positioning accuracy is improved, but incorrect fixing can cause significant position errors and require iterative filter resets
Solution Approach 1:
The patent segments the positioning process into two distinct parts: (1) a low-rate float solution and search process that estimates carrier-phase ambiguities and produces position fixes at a lower rate (e.g., 1 Hz), and (2) a high-rate single-differenced delta phase process that computes position updates at a higher rate (e.g., 10 Hz). This segmentation allows each process to operate optimally for its specific purpose, reducing the risk of incorrect ambiguity fixing while maintaining high update rates.
Solution Approach 2:
The patent performs preliminary ambiguity estimation and position fix generation at a lower rate before using those results to seed the high-rate delta phase updates. The float solution and search process prepares ambiguity estimates in advance, which then serve as initial values for the faster position update process, allowing the system to achieve both accuracy and speed without the pitfalls of incorrect fixing.
2Productivity
If high update rate positioning is implemented, then productivity is improved, but device complexity increases due to processing requirements
Solution Approach 1:
The patent divides the processing workload into two segments: a computationally intensive but low-rate float solution and search process, and a lighter but high-rate single-differenced delta phase process. By segmenting the processing tasks, the system can perform complex ambiguity resolution at a lower rate while maintaining simple, fast position updates at high rates, thus achieving high productivity without proportionally increasing device complexity.
Solution Approach 2:
The patent applies partial action by using the high-rate delta phase process to compute only the position updates (changes in position) rather than recomputing the entire position solution from scratch. This partial computation approach reduces the processing burden at high update rates while still achieving the desired productivity, avoiding the need for excessive computational complexity.
3Loss of time
If float solution and search process is used, then convergence speed is improved, but position errors accumulate in delta phase estimates
Solution Approach 1:
The patent segments the positioning computation into two stages: (1) a float solution and search process that quickly estimates carrier-phase ambiguities and produces initial position fixes at a lower rate, achieving fast convergence, and (2) a single-differenced delta phase process that maintains position accuracy by computing updates relative to the last fixed position, thereby reducing error accumulation. This segmentation allows the system to benefit from both fast convergence and high precision.
Solution Approach 2:
The patent implements feedback by using the results of the float solution and search process to seed and correct the delta phase updates. The high-rate position updates are continuously fed back to the lower-rate ambiguity estimation process, which adjusts its estimates accordingly. This feedback mechanism ensures that position accuracy is maintained while preserving the speed of convergence, preventing error accumulation in the delta phase estimates.
Data Source
AI summary
Methods and apparatus are presented for determining a position of an antenna of a GNSS rover from observations of GNSS signals collected at the antenna over multiple epochs and from correction data for at least one of the epochs. A first-epoch rover position relative to a moving base location is determined, a second-epoch update of the first-epoch rover position relative to the moving base location for a second epoch is determined using a single-differenced delta phase process, and the first-epoch position and the second-epoch update are combined to obtain a second-epoch rover position relative to a moving base location of the second epoch.