GNSS Satellite Line-of-Sight Detection for Multipath Filtering
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Solution Overview
Problem
GNSS receivers face significant inaccuracies due to multipath interference caused by wireless signals reflecting off objects, leading to erroneous measurements and distorted correlation functions.
Innovation Solution
The method involves capturing images near the GNSS receiver to segment the vertical hemisphere into regions based on RF obstruction characteristics and projecting satellite positions onto these regions, allowing for differential processing of signals to distinguish between line-of-sight and reflected signals, using a combination of imaging devices and dual or triple-element GNSS antennas to determine orientation and weight signals accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If all received GNSS signals are processed uniformly, then the processing is simple, but measurement precision deteriorates due to multipath interference from reflected signals
Solution Approach 1:
The patent segments the sky view into multiple regions using an imaging device, where each region is characterized by different RF obstruction properties. By dividing the sky into regions (e.g., obstructed vs. unobstructed), the system can apply different processing weights to signals from different satellite regions, thereby improving positioning accuracy by excluding multipath-contaminated signals without requiring complex individual signal analysis.
Solution Approach 2:
The patent introduces an imaging device as an intermediary tool to detect RF obstructions in the sky. This intermediary device captures images that are then processed to determine region characteristics, which in turn guide the selective processing of GNSS signals. This intermediary approach simplifies the overall system by using a separate detection mechanism rather than directly analyzing signal characteristics for multipath identification.
2Reliability
If signals from all sky regions are processed equally, then device complexity is low, but reliability deteriorates due to inclusion of reflected signals
Solution Approach 1:
The patent applies local quality by assigning different processing characteristics to signals from different sky regions. Instead of uniform processing, signals from regions identified as having RF obstructions are weighted differently or excluded, while signals from clear regions are processed with higher weight. This localized differentiation improves reliability by ensuring that only authentic line-of-sight signals contribute significantly to the positioning calculation.
3Measurement precision
If imaging devices are used to segment the sky into regions, then measurement precision improves, but device complexity increases due to additional sensors and processing
Solution Approach 1:
The patent makes the imaging device serve multiple functions: it captures images for region segmentation, determines orientation data when combined with other sensors, and provides visual documentation of the environment. This multi-functionality justifies the addition of the imaging device by maximizing its utility across multiple aspects of the signal processing system.
Data Source
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AI summary
Disclosed are techniques for processing satellite signals for computing a geospatial position. A plurality of GNSS signals are received from a plurality of GNSS satellites. An image is captured using an imaging device at least partially oriented toward the plurality of GNSS satellites. The image is segmented into a plurality of regions based on RF characteristics of objects in the image. An orientation of the image is determined. The plurality of GNSS satellites are projected onto the image based on the orientation of the image such that a corresponding region is identified for each of the plurality of GNSS satellites. Each of the plurality of GNSS signals is processed in accordance with the corresponding region.