GNSS Receiver State Estimation With Partial Ambiguity Fixing
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Solution Overview
Problem
Existing GNSS positioning methods face challenges in achieving precise and rapid convergence of carrier phase ambiguities due to multipath and residual errors, leading to long computation times and reduced accuracy, especially in areas without a dense reference station network.
Innovation Solution
A method that selects a subset of carrier phase measurements for ambiguity fixing using a recursive state estimator, such as a Kalman filter, to reduce the number of ambiguities to be resolved, by identifying and mapping phase ambiguities to integer numbers while adjusting other parameters based on high-accuracy correction information, thereby reducing computational effort and convergence time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If all carrier phase ambiguities are fixed to integer numbers, then positioning precision is improved, but convergence time increases significantly and computational effort increases
Solution Approach 1:
The patent segments the set of all carrier phase ambiguities into two subsets: a first subset that is fixed to integer numbers and a second subset that remains as floating-point estimates. This segmentation allows the system to achieve partial ambiguity fixing with reduced computational effort and shorter convergence time while still improving positioning precision for the selected subset.
Solution Approach 2:
Instead of fixing all carrier phase ambiguities (excessive action), the patent applies partial action by selectively fixing only a subset of ambiguities that meet specific criteria. This partial fixing approach achieves a balance between positioning precision improvement and acceptable convergence time, avoiding the excessive computational burden of complete ambiguity fixing.
2Measurement precision
If all carrier phase ambiguities are fixed to integer numbers, then positioning precision is improved, but computational effort increases
Solution Approach 1:
The patent divides the ambiguity fixing process into segments by identifying a first subset of carrier phase ambiguities for fixing and a second subset for maintaining as floating-point estimates. This segmentation reduces the computational complexity from fixing all ambiguities to fixing only the selected subset, making the system more efficient while still achieving improved positioning precision.
Solution Approach 2:
The patent applies partial action by fixing only a subset of carrier phase ambiguities rather than all of them. This partial fixing approach reduces computational effort and complexity while still achieving meaningful improvements in positioning precision for the selected subset, avoiding the excessive computational burden of complete ambiguity fixing.
3Measurement precision
If a dense reference station network is used, then positioning accuracy is improved, but infrastructure dependency increases and applicability in remote areas decreases
Solution Approach 1:
The patent extracts the dependency on dense reference station networks by implementing a method that works with undifferenced and uncombined carrier phase measurements without requiring spatial error correlation from nearby reference stations. This extraction of the reference station dependency enables the system to achieve high positioning accuracy in remote areas where dense infrastructure is unavailable.
Solution Approach 2:
The patent introduces precise satellite orbit and clock correction information as an intermediary that replaces the need for local reference station networks. These corrections act as a mediator that enables accurate positioning computations without requiring the traditional infrastructure of dense ground-based reference stations, thereby extending applicability to remote areas.
Data Source
AI summary
A method for determining a state parameter of a global navigation satellite system receiver and an apparatus, in particular its absolute position, determining being based on—a measured information including a pseudorange, a carrier phase and/or a Doppler frequency measurement, —broadcast information on the satellite orbits and clock offsets, and—high accuracy correction information of a satellite positions, clock offsets, code and/or phase biases, the method comprising: —determining a satellite position estimate and a clock offset estimate based on the broadcast information, —determining a corrected satellite position and a corrected clock offset based on the satellite position estimate and the clock offset estimate by using the high accuracy information, in particular the high accuracy correction information of the satellite position and the clock offset.