Upward Facing Sensor for GNSS Obstruction Detection
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Solution Overview
Problem
Location determination using GNSS is subject to various errors such as ionospheric and tropospheric delays, clock synchronization errors, ephemeris errors, and multipath errors, which limit accuracy, especially under obstructed conditions.
Innovation Solution
A method and apparatus are provided to determine the amount of obstruction of a satellite view by using a sensor to extract satellite location measurements, calculating a window of possible locations around the estimated satellite location to account for measurement errors, and determining a likelihood of obstruction based on the overlap of obstructed areas and the window, thereby assigning a weight to the reliability of the satellite signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GNSS receiver uses satellite signals for location determination, then location can be triangulated, but accuracy is limited to a few meters under open sky conditions and becomes worse under limited-view conditions
Solution Approach 1:
An upward-facing camera is introduced as an intermediary device to capture images of the sky and detect obstructions. The camera serves as a mediator between the GNSS receiver and the satellites, providing visual information about the line-of-sight conditions. By processing these images to identify obstructions and calculating obstruction scores, the system can weight or reject satellite signals accordingly, thereby mitigating the harmful effects of multipath errors and improving location determination accuracy.
2Measurement precision
If GNSS receiver tracks more satellites to improve accuracy, then location accuracy can be improved, but under obstructed conditions some satellite signals are unreliable
Solution Approach 1:
The system implements feedback by using the camera to continuously monitor the sky and detect obstructions. The processed image information feeds back to the GNSS receiver to dynamically adjust the reliability weighting of satellite signals. Satellites whose paths are blocked or partially blocked by detected obstructions receive lower weights or are rejected, while satellites with clear paths maintain higher weights. This feedback mechanism ensures that only reliable satellite signals contribute significantly to the location calculation, improving both accuracy and reliability.
3Reliability
If camera is used to detect obstructions, then satellite signal reliability can be assessed, but device complexity increases
Solution Approach 1:
The upward-facing camera serves multiple functions: it detects obstructions for satellite signal assessment, provides visual context for the surveying operation, and can potentially be used for other environmental sensing. By making the camera multi-functional, the patent justifies the added device complexity as the camera contributes to multiple system goals rather than being a single-purpose addition. The camera's image processing pipeline is integrated into the existing GNSS processing workflow, sharing computational resources and reducing overall system complexity.
Data Source
AI summary
Disclosed are a method and apparatus are provided for determining the amount of obstruction of a view of a satellite. An estimated satellite location from a satellite signal is mapped to a matrix of obstructions. A window is determined around the satellite location and all the obstructions within the window are considered in determining whether the satellite is obstructed, with the window considering the degree of possible error within the various measurements. In embodiments, the window size if varied based on the estimated amount of error and location of the satellite within the matrix.