Selective GNSS Signal Filtering for Multipath Navigation Errors
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Solution Overview
Problem
Global Navigation Satellite System (GNSS) devices face challenges in urban and forested areas due to signal obstruction and multipath errors, which affect the accuracy of position calculations.
Innovation Solution
The system employs selective and opportunistic GNSS navigation by mapping 'open sky' or 'clear sky' locations to received GPS signals, using a database of known open/clear sky areas to filter out suspect signals and improve navigation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional omnidirectional GNSS antennas are used to receive signals from all directions, then signal coverage is maximized, but multipath errors from reflected signals cannot be distinguished from direct signals
Solution Approach 1:
The patent segments the sky view into multiple discrete directions (e.g., 360 degrees divided into multiple sectors). Each sector is independently evaluated for signal quality using clear sky data, allowing the system to selectively accept or reject signals from specific directions. This segmentation enables differentiation between direct and reflected signals by analyzing their directional characteristics.
Solution Approach 2:
The patent applies local quality assessment by evaluating signal characteristics in different sky directions separately. Clear sky data is used to determine which directional sectors provide reliable direct signals versus those likely containing multipath reflections. Each sector receives different weighting or acceptance criteria based on its local quality assessment, improving overall position accuracy.
2Productivity
If signals from all directions are processed equally, then calculation speed is maintained, but position accuracy deteriorates due to inclusion of multipath errors
Solution Approach 1:
The patent performs preliminary action by pre-establishing clear sky data that identifies which sky directions typically provide direct line-of-sight signals versus those prone to multipath reflections. This pre-characterization of the environment allows the system to quickly filter signals during navigation calculations without performing complex real-time analysis, maintaining calculation speed while improving accuracy.
Solution Approach 2:
The patent implements feedback mechanisms where clear sky data and observed signal characteristics are continuously used to adjust signal acceptance criteria. The system monitors signal quality metrics and compares them against expected patterns from clear sky data, providing feedback that refines the selection of valid signals for position calculation, thereby improving accuracy without sacrificing processing efficiency.
Data Source
AI summary
Systems and methods for selective and/or opportunistic GNSS/GPS navigation that actively mask or filter satellite signals based on identified “clear sky” or “obstructed sky” regions.