Urban Navigation Database Using Satellite Visibility Masks
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Solution Overview
Problem
Existing navigation systems, such as GPS, face challenges in accurately determining position in urban environments where buildings and structures inhibit satellite signal acquisition, leading to incomplete or inaccurate location estimates.
Innovation Solution
The method involves creating an enhanced database with satellite signal visibility mask information, which includes expected azimuth/elevation data for potential line-of-sight and non-line-of-sight signal reception, and using probabilistic analysis to estimate position locations by comparing expected and observed satellite reception patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional satellite positioning systems are used in urban environments, then the system structure remains simple, but position accuracy deteriorates due to signal blockages from buildings and structures
Solution Approach 1:
The patent applies preliminary action by pre-computing satellite visibility masks for multiple point locations in the urban area before the positioning operation. The enhanced database stores pre-calculated information about which satellites are visible from each location, considering building blockages. During actual positioning, the mobile device simply queries this pre-computed database and compares expected visibility patterns with observed satellite signals, avoiding real-time complex ray-tracing calculations and significantly improving position accuracy without requiring complex real-time processing hardware.
2Reliability
If satellite signal acquisition is attempted in urban areas with buildings, then complete location estimation is desired, but signal blockages cause incomplete or inaccurate location estimates
Solution Approach 1:
The patent converts the harmful effect of building blockages into a beneficial feature by using the presence and pattern of blockages as positioning information. Instead of treating signal blockages as mere obstructions to be avoided, the system pre-computes visibility masks that capture the unique shadowing pattern created by buildings from each point location. The mobile device then identifies its position by matching the observed pattern of blocked and visible satellites against the pre-computed patterns in the enhanced database, effectively using the harmful blockages as a fingerprint for location identification.
3Measurement precision
If enhanced database with visibility mask information is created, then position accuracy improves in urban areas, but database size and information storage requirements increase
Solution Approach 1:
The patent extracts only the essential positioning information needed for urban canyon navigation from the complete satellite visibility data. Instead of storing full three-dimensional ray-tracing results or complete satellite ephemeris data for every possible location and time, the system extracts and stores simplified visibility mask patterns that indicate which satellites are visible from each pre-defined point location. This extracted information is sufficient for pattern matching and position identification, significantly reducing database size while maintaining the ability to achieve accurate urban positioning.
Data Source
AI summary
A mobile device includes a receiver to obtain three-dimensional geographic information identifying at least one open area and at least a height associated with at least one object adjacent to the at least one open area, determine at least one pathway in the open area, and determine expected line of sight and expected non-line of sight detections of satellite positioning system (SPS) signals at locations along the pathway based on the three dimensional geographic information. The mobile device includes a processing unit to estimate a location of the mobile device based on application of the expected line of sight detections and the non-line of sight detections to signals acquired at the receiver.