GNSS Baseline Determination via Satellite Motion Correction
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Solution Overview
Problem
Low cost GNSS receivers with imprecise receiver clocks struggle to accurately determine the baseline between two receivers due to large clock offsets, rendering existing methods like LAMBDA and phase calibration ineffective for both stationary and moving objects, especially in environments where satellite movement during clock offset is significant.
Innovation Solution
The method estimates individual clock offsets and calculates a clock offset difference to apply a satellite motion correction for double-difference measurements, allowing for precise baseline determination using corrected double differences, which can resolve integer ambiguities even with low cost receivers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If low cost GNSS receivers with imprecise clocks are used, then device cost is reduced, but measurement precision deteriorates due to large clock offsets
Solution Approach 1:
The patent transforms the double-difference measurements by applying a satellite motion correction that compensates for clock offsets. This parameter transformation allows the system to achieve high baseline determination precision despite using low-cost receivers with imprecise clocks, effectively decoupling measurement precision from receiver cost.
Solution Approach 2:
The patent introduces an intermediary correction term based on satellite motion that mediates between the imprecise clock measurements and the desired accurate baseline. This correction acts as a bridge that eliminates the harmful effect of clock offsets without requiring expensive precision clocks.
2Measurement precision
If traditional LAMBDA method is used for integer ambiguity resolution, then baseline accuracy can reach millimeter to centimeter level, but the method becomes inapplicable when clock offsets exceed satellite position precision
Solution Approach 1:
The patent modifies the measurement model by applying a satellite motion correction to the double-difference carrier phase measurements. This parameter change restores the validity of integer ambiguity resolution for low-cost receivers with large clock offsets, extending the applicability of LAMBDA-like methods to a broader range of receiver types.
Solution Approach 2:
The patent introduces dynamic correction terms that account for satellite motion during the clock offset period. This dynamic approach allows the method to adapt to varying clock offset conditions and maintain baseline accuracy across different operational scenarios.
3Measurement precision
If phase calibration method is used to compensate for clock offsets, then baseline determination precision improves, but receiver movement is required which limits applicability to stationary objects
Solution Approach 1:
The patent introduces a satellite motion correction as an intermediary that compensates for clock offsets without requiring receiver movement. This correction term serves as a mediator that achieves the precision benefits of phase calibration while removing the movement requirement, thereby extending applicability to stationary objects.
Solution Approach 2:
The patent replaces the mechanical requirement of receiver movement with a computational satellite motion correction. Instead of physically moving the receiver to calibrate phases, the method uses mathematical correction based on satellite ephemeris data to achieve the same precision effect.
Data Source
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AI summary
In the method for determining a baseline (8) between two receivers (6, 7) of a satellite navigation system (1), the receivers (6, 7) perform measurements on signals emitted by satellites (2) of the satellite navigation system (1). The baseline (8) is then determined by an evaluation unit (11) connected to the receivers (6, 7). The evaluation unit (11) first estimates the individual clock offsets of the receivers (6, 7). A clock offset difference is calculated from the individual clock offsets. The clock offset difference is used for calculating a satellite motion correction for the motion of the satellites (2) during the clock offset difference. For determining the position and orientation of the baseline (8), the evaluation unit (11) uses double-differences of the measurements, wherein the satellite motion correction is used for correcting the double-differences of the measurement resulting in corrected double differences of the measurements. The baseline (8) is finally determined based on the corrected double differences of the measurements. Using this method allows to determine the baseline (8) between two receivers (6, 7) with high precision even if low cost receivers (6, 7) are used that are provided with imprecise receiver clocks.