Navigating the Depths: The Power of Handheld Laser Scanners in Underground Tunnel Mapping

Underground caverns, subterranean pathways - natural or fabricated, you've probably visited one of them. These spaces beneath our feet have existed for almost as long as humans have roamed the earth. For centuries, we've dug ​tunnels to transport goods, keep people safe, build transit networks, direct vital utilities around and between cities, and even exploit deeply-hidden resources and treasures to create the world we live in today. From bunkers and silos that housed pieces of history, to new projects and explorations that give the underground territory new functions and relevance, our interest in understanding and mapping these spaces only grows with time. As we navigate the complexities of what lies below the surface, understanding how to effectively monitor and safeguard these spaces becomes paramount. We will explore how far technology has come over the ages, and how tools like handheld laser scanners have made mapping the underground easier, faster, and safer.

Getting a grasp of what's down below

Parties of interest spend considerable time and ​billions of dollars every year to figure out what's underneath cities. Geological discovery methods aside, traversing and getting a visual representation of a known underground space wasn't always a walk in the park. Before advanced sensors and technology became more commercially available, manual measurements with tape measures and a head lamp were the norm. Later, precise instruments like theodolites and distance meters, as well as ​new technologies like ground-penetrating radar (GPR), electromagnetic location (EML), and, the tool of the hour, SLAM-empowered scanners made their way into surveying the underground. Methods that go beyond 2D drawings like photogrammetry and 3D point cloud modelling also became more accessible, while comprehensive BIM models are also implemented as a standard to monitor data above and below the surface of the ground.

Photo by Martin Brechtl on Unsplash

The evolution of mapping subterranean landscapes has been significantly influenced by the emergence of advanced technologies, particularly handheld laser scanners. These innovative solutions have revolutionized the capture, analysis, and navigation of underground spaces with unprecedented precision and efficiency. One of the most notable advancements is the use of LiDAR (Light Detection and Ranging) scanners, which offer a multitude of benefits for mapping underground environments. LiDAR scanners provide high precision and attention to detail, enabling the detection of key underground features and significantly reducing human errors during the scanning process. Furthermore, LiDAR scanning allows for the rapid acquisition of large amounts of relatively complete spatial data, making it an ideal solution for efficiently mapping underground tunnels and spaces. The technology's ability to create detailed point clouds of scanned areas, coupled with its ease of use and efficiency, makes it a transformative tool for capturing and analyzing subterranean environments.

Benefits of using handheld LiDAR scanner solutions

Real-time detection and progress monitoring

Traditional mapping methods often struggle to keep pace with the dynamic nature of underground environments. Handheld laser scanners, equipped with Simultaneous Localization and Mapping (SLAM) technology, provide real-time data acquisition. This ensures accurate monitoring of tunnel structures, allowing operators to stay informed and in control of the construction progress or as-built conditions.

Faster volume calculation and dimensional measurement

Accurate volume calculations are crucial for resource planning and optimizing operational efficiency. Handheld laser scanners facilitate precise volume calculations and distance measurements, providing valuable insights for project managers and engineers. Rapid dimensional measurements of cavities, including corridor width and height, contribute to efficient and detailed mapping, which is particularly valuable for infrastructure and construction projects.

Seamless digitization and data management

  

Creating a digital representation of underground spaces is fundamental for effective planning and decision-making. Handheld laser scanners excel in capturing high-resolution, three-dimensional data, allowing for the creation of detailed and accurate digital models of tunnel structures. A quick mesh model allows operators to visualize the underground space, measure, and calculate dimensions for more effective management.

High operational flexibility

Handheld laser scanners work in environments where GPS or GNSS signals are not accessible, expanding their utility to underground spaces and other GPS-denied areas. Moreover, scanners often have the option of integrating with an RTK rover to produce georeferenced measurements, enabling the generation of highly accurate 3D maps of the environment.

Applications and use cases

The benefits of laser scanning, particularly the high data precision, reduced time, labor, and human errors, and the richness of point cloud data, have significantly transformed the way spatial data is captured in underground environments. This has led to improved safety, efficiency, and decision-making in various industries, including mining and underground construction project management. Let's take a look at some real-world applications.

Gold mine in Jiangxi, China

A client in China's Jiangxi Province leveraged 3D data generated using the FJD Trion S1 for real-time monitoring, progress tracking, safety hazard identification, volume calculations, and distance measurements within the underground mine space.   

This digitalization is essential for ensuring efficient and safer mine operations, as well as for complying with regulatory requirements. The use of advanced technologies such as LiDAR scanners enable the rapid and accurate mapping of underground environments, providing detailed spatial data that is essential for various applications, including safety inspections, infrastructure planning, and ongoing mine operations, allowing for better decision-making, improved safety, and optimized production cycles.

Japan - digitized tunnel models for repairs and maintenance

In Hokkaido, Japan, our client sought an innovative approach to streamline regular maintenance for an aging tunnel. Before incorporating the FJD Trion S1 scanner into their workflow, the tunnel's digital documentation relied on camera drones. However, these drones fell short in providing the comprehensive 3D data and thickness required for a thorough tunnel model.

Opting for the handheld SLAM scanner, the client aimed to enhance their data capture capabilities, ensuring a more detailed representation of the tunnel's structure. The FJD Trion S1 emerged as the ideal solution, offering a cost-effective, user-friendly setup and operation process. Its accurate and colorized data output enabled the client to identify and assess gaps as small as 5-10cm, empowering them to monitor the tunnel's condition comprehensively and efficiently flag any areas of concern throughout its lifecycle.

Belgium - A 3D Inventory of Quarries

An over 2000 ㎡ section of old sandstone mines located in the community of Riemst, Flanders, Belgium, was scanned using the FJD Trion P1 in less than 15 minutes. The flexibility and efficiency of the solution enabled the client to prove that the use of P1 could be a viable option for larger scale operations in digitizing tunnel records.

The 3 main reasons to digitize these tunnels are:

1. An accurate inventory and digital records can help municipalities with effective governance and urban planning. Detailed topographical maps that contain the locations, dimensions, and interconnections of tunnels, provide a comprehensive overview for municipal authorities. They can also easily refer to the conditions of tunnels to assess potential risks and prioritize maintenance or conservation efforts.
2. Integrating the laser scans with surface-level geographical data allows for comprehensive analysis. For instance, it enables the detection of structures, such as a house or road, positioned directly above an underground mine. This information empowers proactive measures within the mine, such as stabilization efforts or the construction of supportive structures, to prevent potential stability issues or the risk of collapse for the overlying structures, such as houses or roads.
3. Heritage preservation. Detailed digital maps can capture the intricate details of mining structures, equipment, and landscapes. Historical artifacts and features within mines can be digitally preserved in their original context, providing a virtual archive for education, research, and even virtual tours.

Final Thoughts

In the ever-evolving landscape of mining and tunneling, the integration of handheld laser scanners marks a significant leap forward. These devices, with their real-time capabilities, safety enhancements, and precise measurements, empower professionals to navigate the complexities of underground spaces with confidence. As industries continue to prioritize digitization and safety, the adoption of SLAM-based handheld laser scanners is poised to be a game-changer. Embrace the future of underground mapping with these cutting-edge technologies.

Head over to this guide to learn how to choose a scanner that fits your needs.

A handheld solution like the FJD Trion S1 is a versatile option that prioritizes scanning efficiency with a range of up to 120 m and compatibility with an RTK receiver for geo-referenced point cloud and a 360 camera for colorized models.

Learn More about S1

The lightweight and compact FJD Trion P1 is about the same size and weight as a large water bottle. While its footprint is small, no compromises were made in making it a powerful tool to capture crisp point clouds, even colorized ones.

Learn More about P1