Case Study: Why HRT chose Teledyne’s mobile mapping spherical camera for Taipei Metro’s tunnel inspection systems

Summary

This customer story describes how HRT® Corporation helped Metro Taipei® (TRTC) update its tunnel inspection process by combining 2D LiDAR with Teledyne® 360-degree imaging system. It outlines challenges with traditional measurement methods, the value of adding 360° high resolution visuals to LiDAR data, and improvements in efficiency and safety. The case also demonstrates the real-world benefits of Teledyne Ladybug® camera series for railway infrastructure maintenance.

Table of Contents

• Introduction

• Challenges

• 2D LiDAR Integration with Ladybug5+

• HRT’s Client Impact

• Conclusion

Ladubug5Plus mounted on a high speed metro line.

Introduction

Founded in 2012, HRT Corporation provides measurement and monitoring solutions for aviation, automotive, and maritime applications. The company supports clients with system design, equipment selection, data integration and analysis, to boost quality and efficiency.

HRT and Taipei Metro

HRT designed and integrated a vehicle-based railway inspection system for Taipei Metro (TRTC), to support infrastructure monitoring and maintenance. The system is used by the Taipei Metro's Preventive Maintenance Section, within the Rolling Stock Department, to conduct annual tunnel clearance gauge measurements. This critical safety task ensures the tunnels remain within set spatial limits so trains can operate safely and reliably across the network.

Metro Tunnel Clearance Safety Requirement

Taipei Metro operates in a dense and tightly constrained tunnel environment. Infrastructure elements such as cables, pipes, and platform edges must always remain clear of the train’s defined clearance envelope to ensure safe operations.

Clearance gauge measurement is essential for ensuring a safe margin. It is used to:

1. Monitor the spatial relationship between rolling stock and surrounding structures
2. Detect potential encroachments before they develop into safety risks
3. Support preventative maintenance planning and ongoing operational safety assurance.

Challenges

Limitations of Existing Measurement Methods 

Before deploying the new system, Taipei Metro used a vehicle-based 2D LiDAR scanner to capture clearance profiles. Although this method provided accurate measurements, it only produced two-dimensional data. Without a correct visual context of the tunnel, the operators could not identify what was causing the clearance violations. The existing LiDAR system was also discontinued, raising concerns about long-term system sustainability.

Complexity of Alternative Technologies

During system development, HRT evaluated alternative sensing technologies and determined that:

1. 3D LiDAR point clouds are affected by train speed, producing complex data patterns
2. Processing these data sets for clearance inspection adds unnecessary complexity
3. This level of complexity wouldn’t align with the practical requirements of routine clearance measurement

2D LiDAR with Ladybug5+ Mobile Mapping System

To address these challenges, HRT developed an Integrated Monitoring System that combines 2D LiDAR with a 360‑degree spherical imaging system using Teledyne’s Ladybug camera series.

Why Teledyne’s Spherical Imaging Camera

During development, the integration of a Ladybug spherical imaging camera was identified as the ideal solution for the application. The Ladybug5+ camera provides:

1. Full 360‑degree visual coverage of the tunnel environment
2. Simultaneous visibility of the left and right sides of the inspection vehicle
3. High‑resolution imagery of areas where encroachments are most likely to occur, including cables, pipes, and platform edges

Complementary Roles of LiDAR and Imaging

In the integrated system each sensor plays a clear role. The 2D LiDAR provides precise clearance profiles, while the Ladybug5+ imagery adds visual context, allowing operators to:

1. See the real‑world tunnel environment with measurement data
2. Identify and confirm specific objects affecting clearance conditions

This approach keeps LiDAR measurement reliable and adds environmental context.

HRT’s Client Impact

The integrated system enabled Taipei Metro to:

1. Perform annual clearance gauge measurements as part of its preventative maintenance program
2. Monitor clearance envelopes while maintaining operational safety
3. Visually verify potential encroachments within the tunnel environment
4. Improve interpretability of inspection results by pairing geometry with imagery

Additional advantages of the new integrated system

Equipment weight: The new system weighs one-third to one-half of the original system, making installation and disassembly easier.
Relevant data: Operators can review Ladybug5+ images from five seconds before and after key timing points.
Warranty: Core system components are backed by device manufacturer warranties.

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Conclusion

By combining 2D LiDAR with Teledyne’s Ladybug spherical imaging, HRT delivered a practical inspection solution tailored to real‑world railway operations. 

Early collaboration with Teledyne imaging experts helped streamline system development and ensure the right technology choices from the start. 

This approach accelerated development and improved outcomes of HRT Corporation, while delivering long-term value for Taipei Metro.