GNSS Ambiguity Selection via Weighted Candidate Averaging
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Solution Overview
Problem
Current GNSS positioning systems face challenges in achieving rapid and precise position estimation due to the integer ambiguity problem, which limits the accuracy of carrier phase measurements and requires lengthy convergence times for float solutions.
Innovation Solution
The method involves selecting candidate sets for a weighted average based on quality measures, allowing for rapid convergence to the correct integer solution without fixing ambiguities, using a filter to estimate float ambiguities and assigning integer values to form candidate sets, and calculating a weighted average of these sets to improve precision and speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If carrier phase measurements are used to improve positioning precision, then measurement precision is improved, but the integer ambiguity problem arises causing reliability to deteriorate
Solution Approach 1:
The patent applies preliminary action by using code-based positioning to obtain an initial position estimate before carrier phase measurements are fully processed. This initial estimate serves as a starting point for resolving integer ambiguities in the carrier phase data, enabling the system to achieve centimeter-level precision without being trapped in the ambiguity problem. The preliminary code-based position provides a reliable reference that guides the subsequent carrier phase ambiguity resolution.
2Measurement precision
If float solutions are used to resolve ambiguities, then positioning accuracy is improved, but convergence time increases causing productivity to deteriorate
Solution Approach 1:
The patent uses code-based positioning to obtain an initial position estimate that serves as a starting point for carrier phase ambiguity resolution. This preliminary action provides a reliable initial state that accelerates the convergence of float solutions, reducing the time required to achieve centimeter-level precision without sacrificing accuracy.
Solution Approach 2:
The patent introduces code-based position estimates as an intermediary element that bridges the gap between raw carrier phase measurements and final precise positioning. This intermediary provides a reliable initial position that facilitates faster convergence of the ambiguity resolution process, acting as a mediator that enables rapid acquisition of precise positions.
3Measurement precision
If ambiguities are fixed to integer values, then positioning precision is improved, but the risk of incorrect fixing increases causing reliability to deteriorate
Solution Approach 1:
The patent applies preliminary code-based positioning to obtain an initial position estimate before fixing ambiguities. This preliminary action provides a reliable reference frame that guides the ambiguity fixing process, ensuring that integer values are assigned correctly based on the initial position context, thereby reducing the risk of incorrect fixing while maintaining centimeter-level precision.
Data Source
AI summary
Methods and apparatus are provided for estimating parameters, i.e. ambiguities, derived from GNSS signals. Observations of a GNSS signal from each of a plurality of GNSS satellites are obtained (4120). The observations are fed to a filter having a state vector at least comprising a float ambiguity for each received frequency of the GNSS signals, each float ambiguity constituting a real number estimate associated with an integer number of wavelengths of the GNSS signal between a receiver of the GNSS signal and the GNSS satellite from which it is received, and the filter being for estimating a float value for each float ambiguity of the state vector (4140). A subset of float ambiguities of the state vector is selected (4150). Integer values are assigned to the estimated float values of the float ambiguities of the subset to define a plurality of integer ambiguity candidate sets (4160). A quality measure is determined for each of the candidate sets. A weighted average of the candidate sets is formed (4200). Ambiguities of the weighted average can be used in subsequent operations to aid in determining a position of the receiver or can be used to prepare data, e.g., in a network processor that can be used to augment position information of a rover.