GNSS Carrier Phase Ambiguity Resolution via Probabilistic Cost Function
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current Global Navigation Satellite System (GNSS) technologies face challenges in resolving integer ambiguities, especially in urban environments and due to multipath errors, leading to loss-of-lock and cycle slips, which affect positioning accuracy and reliability.
Innovation Solution
A method and system that utilize a probabilistic approach to estimate carrier phase ambiguities by defining a probability density function based on noise characteristics, allowing for the evaluation of all possible integer values and selecting the best fit using multiple Kalman filters to track the receiver's position, thereby resolving ambiguities outside of the Kalman filter framework.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If linear estimation methods are used to estimate integer ambiguities, then the calculation process is simplified, but the accuracy deteriorates because the equations are nonlinear and multiple ambiguity values may be equally likely
Solution Approach 1:
The patent transforms the nonlinear integer ambiguity estimation problem into a linear search problem by defining a cost function that evaluates candidate ambiguity values. Instead of directly solving nonlinear equations, the method changes the approach to evaluating multiple candidate solutions using a probabilistic cost function, thereby simplifying the computational process while maintaining accuracy through systematic evaluation of all plausible integer candidates.
2Area of stationary object
If the receiver separation distance increases, then the coverage area increases, but the reliability of ambiguity resolution deteriorates due to growing distance-dependent biases
Solution Approach 1:
The patent replaces the traditional mechanical approach of minimizing baseline length for reliable ambiguity resolution with a probabilistic evaluation system. By using a cost function that incorporates statistical models of measurement errors and biases, the system can evaluate candidate ambiguity values even when distance-dependent biases are significant, thereby maintaining reliability across larger coverage areas without being constrained by baseline length.
3Ease of manufacture
If commercial positioning systems are used, then the system cost is reduced, but the ability to resolve ambiguities deteriorates in the presence of significant multipath errors or unmodeled systematic biases
Solution Approach 1:
The patent introduces an intermediary cost function evaluation step between raw measurement data and final ambiguity resolution. This cost function acts as a mediator that systematically evaluates candidate ambiguity values while accounting for multipath errors and unmodeled biases through probabilistic modeling. This intermediary layer enables commercial systems to achieve improved ambiguity resolution capability without requiring expensive specialized hardware, bridging the gap between cost-effective commercial systems and high-performance ambiguity resolution.
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A positioning system for a global navigational satellite system (GNSS) includes a receiver to receive carrier signals and code signals transmitted from a set of GNSS satellites that include a carrier phase ambiguity as an unknown integer number of wavelengths of the carrier signal travelled between the satellite and the receiver, and a processor to track a position of the receiver. The processor is configured to determine a set of possible combinations of integer values of the carrier phase ambiguities consistent with the measurements of the carrier signal and the code signal according to one or combination of the motion model and the measurement model within bounds defined by one or combination of the process noise and the measurement noise and execute a set of position estimators determining positions of the receiver using different combinations of integer values of the carrier phase ambiguities selected from the set of possible combinations. Next, the processor determines the position of the receiver using a position estimator with the highest joint probability of the position of the receiver according to the measurements of the carrier and the code signals.