GNSS Receiver Positioning with Motion-Compensated Correlation
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Solution Overview
Problem
Existing GNSS carrier wave processing techniques, such as RTK and PPP, struggle with multi-path effects in urban environments, leading to erroneous positioning solutions due to low update rates of motion-compensated correlation, which prevent accurate determination of integer ambiguities and sub-wavelength accuracy.
Innovation Solution
A method and apparatus that generate a motion-compensated correlation signal at a higher rate than the receiver's movement, combining sensor data with motion-compensated correlation signals to provide accurate frequency shift and phase measurements, enhancing line-of-sight signal detection and mitigating multi-path interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If motion-compensated correlation is used at low update rates, then processing complexity is reduced, but positioning accuracy and integer ambiguity determination are compromised
Solution Approach 1:
The system performs preliminary motion compensation using sensor data at high rates to predict receiver position and velocity. This preliminary action prepares the correlation process by pre-calculating Doppler shifts and phase corrections, enabling the subsequent correlation to be performed at lower rates while maintaining accuracy for integer ambiguity resolution.
Solution Approach 2:
The system dynamically adapts the correlation update rate based on motion characteristics. During periods of low motion or stable conditions, correlation is performed at lower rates. During periods of high motion or when integer ambiguity resolution is critical, the system increases the correlation update rate to maintain positioning accuracy.
2Measurement precision
If carrier-phase positioning is used, then positioning resolution is improved to centimetre-level, but the integer ambiguity problem increases solution time to minutes
Solution Approach 1:
The system performs preliminary measurements using code-phase positioning to establish an initial position estimate. This preliminary action provides a starting point that constrains the search space for integer ambiguity resolution in carrier-phase positioning, significantly reducing the time required to converge on a solution while maintaining centimetre-level accuracy.
Solution Approach 2:
The system uses code-phase positioning measurements as an intermediary to bridge the gap between coarse metre-level positioning and fine centimetre-level carrier-phase positioning. The code-phase solution serves as a mediator that provides initial constraints, enabling faster convergence of the carrier-phase integer ambiguity resolution process.
3Measurement precision
If correction data from reference stations is used, then positioning accuracy is improved, but multi-path effects cannot be corrected in urban environments
Solution Approach 1:
The system segments the signal processing into separate correlation operations for different signal paths. By performing individual correlations for line-of-sight signals and multi-path signals, the system can identify and selectively process direct signals, even in urban canyons with significant multi-path interference, maintaining accuracy where traditional RTK fails.
Solution Approach 2:
The system dynamically switches between RTK correction data and autonomous motion-compensated correlation based on signal quality and environment. In urban environments with multi-path effects, the system transitions to autonomous operation using high-rate sensor data and motion compensation, adapting to conditions where reference station corrections become unreliable.
4Ease of operation
If code-phase positioning is used, then metre-level accuracy is achieved, but carrier wave information for higher precision is underutilized
Solution Approach 1:
The system implements a universal positioning framework that handles both code-phase and carrier-phase positioning through a unified motion-compensated correlation architecture. This multi-functional system can operate in code-phase mode for metre-level accuracy or carrier-phase mode for centimetre-level accuracy, adapting to different operational requirements and signal conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables sub-wavelength accurate positioning solutions with increased robustness to signal outages and cycle slips, even in challenging environments, by ensuring accurate determination of integer ambiguities and enhancing signal detection.
Implementation Method 1
A receiver generates a local replica of the transmitted signal, including the PRN code, and generates a correlation signal by correlating the local replica signal with the received signal
Implementation Method 2
providing motion compensation of at least one of the local signal, the received signal, and the result of the correlation, based on the measured or assumed movement of the receiver
Data Source
AI summary
A method comprising receiving, at a receiver, a plurality of signals from at least one remote source and selecting at least one selected signal in the plurality of signals. The method determines, using the at least one selected signal, a position of the receiver and receives correction data for improving the position of the receiver to a sub-wavelength accuracy. The method further determines motion of the receiver, generates, from the at least one selected signal, a motion-compensated correlation signal based on the determined motion of the receiver and uses the motion-compensated correlation signal to either (1) select the at least one selected signal to be used to determine the position of the receiver, (2) correct at least one of motion sensor errors or clock errors, or (3) both (1) and (2). Embodiments include a positioning system for performing the method.