LiDAR Tunnel Mapping Using Coordinate Transformation
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Solution Overview
Problem
Existing tunnel mapping systems face challenges in achieving precise geodetic positioning within underground transportation tunnels where GPS signals are not available, which is critical for ensuring operational safety and accurate infrastructure characterization.
Innovation Solution
A process utilizing a Hi-Rail vehicle equipped with a LiDAR unit, mobile GPS, inertial navigation system, and speed sensor, combined with stationary GPS, image-identifiable targets, and ancillary corrections from pre-defined tunnel geometry and static LiDAR data, to produce highly accurate three-dimensional mappings of tunnel features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mobile LiDAR mapping systems rely on GPS for geodetic positioning, then positioning accuracy is improved in open environments, but GPS signal availability deteriorates in underground tunnels
Solution Approach 1:
The patent introduces an intermediary coordinate transformation system that converts LiDAR measurements from vehicle-relative coordinates to tunnel-relative coordinates using a series of transformation matrices (rotation, translation, and scaling). This mediator system replaces the direct GPS positioning approach, enabling accurate 3D mapping in tunnels where GPS signals are unavailable by relying on relative measurements and known tunnel geometry parameters.
Solution Approach 2:
The patent performs preliminary actions by collecting tunnel geometry parameters (curvature, grade, superelevation) and establishing the coordinate transformation relationships before conducting the LiDAR survey. The system pre-configures the transformation matrices and tunnel reference frame based on design drawings or preliminary surveys, enabling accurate positioning without real-time GPS signals during the actual tunnel mapping operation.
2Measurement precision
If multiple correction systems (mobile GPS, INS, image targets, ancillary corrections) are integrated to achieve high accuracy in tunnels, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple correction systems (mobile GPS, inertial navigation system, image-identifiable targets, and ancillary corrections from tunnel geometry) into a unified coordinate transformation framework. All these systems contribute data that are integrated through mathematical transformation matrices to achieve accurate 3D mapping, reducing the need for separate independent correction processes while maintaining high measurement precision.
Solution Approach 2:
The patent transforms the correction approach by changing from direct GPS coordinate correction to parameter-based coordinate transformation. The system uses transformation parameters (rotation angles, translation vectors, scaling factors) derived from tunnel geometry and sensor data to adjust the LiDAR point cloud coordinates, replacing complex multi-system GPS/INS integration with a more manageable parameter transformation approach.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the collection of highly accurate, geodetically correct three-dimensional data within tunnels, even without GPS signals, by adjusting point cloud datasets using mobile GPS, inertial navigation, speed data, and ancillary corrections, ensuring precise spatial representation and enhancing safety and maintenance operations.
Implementation Method 1
a surveying method that measures distance to a target by illuminating the target with pulsed laser light and measuring the reflected pulses with a sensor
Implementation Method 2
measures distance to a target by illuminating the target with pulsed laser light and measuring the reflected pulses
Data Source
AI summary
A process for constructing highly accurate three-dimensional mappings of objects along a rail tunnel in which GPS signal information is not available includes providing a vehicle for traversing the tunnel on the rails, locating on the vehicle a LiDAR unit, a mobile GPS unit, an inertial navigation system, and a speed sensor to determine the speed of said vehicle. A stationary GPS, whose geolocation is well-defined, is located near the entrance of the tunnel. Image-identifiable targets having a well-defined geodetic locations are located at preselected locations within the tunnel. The vehicle traverses the tunnel, producing mass point cloud datasets along said tunnel. Precise measurements of 3D rail coordinates are also obtained. The datasets are adjusted based on the mobile GPS unit, the inertial navigation system, the speed sensor, the location of the image-identifiable targets, and the precise measurements of 3D rail coordinates, to thereby produce highly accurate, and substantially geodetically correct, three-dimensional mappings of objects along the tunnel.