Dual Estimator Navigation System for Positioning Precision
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Solution Overview
Problem
Current navigation satellite systems face limitations in achieving precise position estimation due to errors such as ionospheric and tropospheric effects, ephemeris errors, and multipath propagation, especially with code-based positioning methods, and there is a need for improved real-time kinematic (RTK) positioning to enhance productivity.
Innovation Solution
The implementation of a method using a timely estimator and a precise estimator, where the precise estimator is delayed by at least one receiver epoch, allowing for the transfer of precision to the timely estimator, enabling more accurate navigation solutions by recurrently replacing state variables with values computed by the precise estimator, and incorporating observations from both NSS signals and external information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If carrier phase measurements are used for positioning, then measurement precision is improved, but device complexity increases due to the integer ambiguity problem
Solution Approach 1:
The estimation process is divided into two separate filters: a timely estimator that provides rapid but less precise position estimates, and a precise estimator that computes accurate carrier phase measurements by resolving integer ambiguities. This segmentation allows each filter to specialize in one aspect, reducing the complexity burden on any single component while achieving both speed and precision in the overall system.
Solution Approach 2:
The precise estimator acts as an intermediary that processes delayed carrier phase measurements to resolve integer ambiguities and generate corrected state variables. These corrected variables are then transferred to the timely estimator, serving as a bridge that transfers precision from the precise estimator to the timely estimator without requiring the timely estimator to directly handle the complex ambiguity resolution.
2Measurement precision
If precise estimator with delayed processing is used, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The system segments the estimation function into two parallel filters with different timing characteristics. The timely estimator operates with minimal delay to provide immediate position estimates, while the precise estimator accepts a deliberate delay to perform comprehensive carrier phase processing. This segmentation allows the system to tolerate delay in one path while maintaining responsiveness in the other.
Solution Approach 2:
The system implements a feedback mechanism where the precise estimator's corrected state variables are transferred back to the timely estimator. This feedback loop allows the timely estimator to periodically refresh its state variables with precise corrections, effectively reducing the impact of delay by ensuring that the most recent precise corrections are applied to maintain accuracy without requiring continuous delayed processing.
Data Source
AI summary
The invention relates to a method carried out by a navigation satellite system (NSS) receiver or a processing entity receiving data therefrom, for estimating parameters useful to determine a position. The NSS receiver observes NSS signals from NSS satellites over multiple epochs. A first filter, called “timely estimator”, and second filter, called “precise estimator” and delayed with respect to the timely estimator, are operated. The estimators use state variables, and make use of NSS signals observed by the NSS receiver or information derived therefrom. The precise estimator further computes its state variable values based on observations that are not derived from NSS signals observed by the NSS receiver. The values of some of the state variables computed by the timely estimator are recurrently replaced by values from the precise estimator. A corresponding system is also disclosed.