Constrained-Route GNSS Error Characterization for Urban Rail Positioning
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Solution Overview
Problem
GNSS receivers in constrained vehicles, such as trams and trains, experience significant positioning errors due to urban environments, leading to inaccurate location estimates, which are not adequately addressed by conventional methods.
Innovation Solution
Utilizing a constrained apparatus onboard the vehicle to determine a GNSS-based position estimate and calculate an error characterization based on the expected location along the constrained route, incorporating IMU and radio interface observations, to correct the positioning errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GNSS receiver data is used for positioning in urban environments, then positioning coverage is improved, but position accuracy deteriorates to only 5-10 meters due to limited signal availability and multipath effects
Solution Approach 1:
The patent introduces an intermediary system consisting of reference receivers positioned at known locations throughout the urban environment. These reference receivers act as mediators between the GNSS satellites and mobile receivers, providing correction data that compensates for multipath effects and signal availability issues. The reference receivers establish a local reference frame that enables accurate positioning without requiring direct line-of-sight to satellites from every location.
Solution Approach 2:
The system implements feedback by continuously monitoring the difference between expected positions (based on known reference locations) and actual GNSS-derived positions. This feedback loop allows the system to calculate correction values that are then applied to mobile receiver positions, systematically reducing the 5-10 meter accuracy error mentioned in the problem statement.
2Measurement precision
If error characterization is calculated and applied to correct mobile device positions, then navigation accuracy is improved, but device complexity increases due to the need for error characterization calculations and corrections
Solution Approach 1:
The patent segments the positioning system into distinct functional components: reference receivers that collect data at known locations, a processing system that calculates error characterizations, and mobile receivers that apply corrections. This segmentation allows the complex error characterization calculations to be performed by dedicated reference infrastructure rather than by every mobile device, reducing the computational burden on mobile devices while maintaining high navigation accuracy.
Solution Approach 2:
The system performs preliminary actions by pre-calculating error characterizations at reference locations before mobile devices need them. The reference receivers continuously establish error models for their locations, so when mobile devices pass through these areas, the error corrections are already prepared and available for immediate application, reducing the real-time computational requirements for mobile devices.
Data Source
AI summary
One or more processors obtain GNSS receiver data captured during a time period by a GNSS receiver disposed onboard a constrained vehicle traversing a constrained route. The processor(s) determine a GNSS-based position estimate based on the GNSS receiver data. The position estimate indicates an estimated location of the GNSS receiver during at least a portion of the time period. The processor(s) determine an error characterization corresponding to an offset between the position estimate and an expected location of the GNSS receiver along the constrained route. The processor(s) cause a mobile device to perform a positioning or navigation-related function that accounts for the error characterization.