By Karl Bradshaw, Contributing Author
Advanced reality capture technologies has become fundamental to the surveyor’s toolbox for cost-effective infrastructure management.
Particularly well suited for tunnel work, mobile mapping and scanning promise significant improvements in efficiency, accuracy and overall project success as the demand for asset inspection and rehabilitation grows.
The 360-degree panoramic image/point cloud generated by a mobile mapping system provides valuable context to the data.
Leveraging mobile mapping solutions in tunnels is advantageous for stakeholders to minimize traffic interruptions, ensure early detection of problem areas and expedite repairs and upgrades.
Tunnels, whether newly constructed or aging, require meticulous oversight to ensure safety, operational efficiency and longevity.
Traditional methods of inspection and management often involve manual surveys, which are labor-intensive, time-consuming and prone to inaccuracies.
In contrast, mobile mapping technology revolutionizes this approach by enabling rapid, comprehensive data collection with advanced sensors and imaging systems without disrupting traffic.
In a two-part inspection process, the mobile mapping system may be used at regular intervals, quarterly or annually, to map the tunnel assets. This data is analyzed for the initial detection of catastrophic flaws such as leaks and cracks and followed up with terrestrial scanning as necessary.
Further analysis will pinpoint an area to be monitored more frequently with an automated system.
Benefits of Mobile Mapping
Comprehensive Data Capture: Mobile mapping systems integrate high-resolution imaging, LiDAR (Light Detection and Ranging) and highly accurate motion and positioning technologies to capture detailed 3D data of tunnel interiors and exteriors.
When combined with traditional survey control points and networks the produced deliverable is a context-rich and accurate data set. This holistic approach ensures that every structural detail is documented with precision.
Efficiency and Safety During Data Collection: By mounting these systems on mobile platforms or vehicles, engineers can efficiently survey vast tunnel networks in a fraction of the time required by traditional methods.
After completing comprehensive mapping with a mobile mapping system, a terrestrial scanner can be employed for specific areas as necessary. This efficiency minimizes disruption to traffic and tunnel operations and limits exposure of workers to danger. The ease of use encourages more frequent monitoring and provides confidence that maintenance is performed in a timely manner.
Enhanced Accuracy: Traditionally, inspectors may review the whole tunnel or selected sections with a tape measure — a time-consuming process prone to human error and subjectivity. Instead, the data acquired through mobile mapping is collected much more quickly and is not only extensive but also highly accurate.
With the addition of control point-based targets and automated registration methods, mobile mapping assures cm-level accuracy. The system delivers an accurate point cloud of the environment along with complementary 360-degree imagery providing substantial gains in productivity.
Cost-Effectiveness: While initial investments in mobile mapping technology can be substantial, the long-term savings are significant. Reduced labor costs, faster project turnaround times and proactive maintenance scheduling contribute to overall cost-effectiveness and a positive return on investment.
The full integration of mobile mapping data with advanced processing software creates a complete field-to-finish workflow that turns data into actionable information easily accessible to stakeholders.
Faster Analysis and Decision Making: Advanced software tools process this data to create detailed 3D models, identify anomalies and facilitate condition assessments. In Trimble Business Center (TBC), deep learning-based classification algorithms specifically for tunnels speed up analysis by separating relevant information from noise.
Clean data is the foundation for structured maps, heat map comparisons, deformation comparisons and other feature extraction operations. Key insights extracted based on evidence rather than human perception empower engineers to make informed decisions regarding maintenance, repairs and future upgrades.
Supporting Rehabilitation
Beyond routine inspections, reality capture with mobile mapping plays a critical role in supporting rehabilitation and construction activities within tunnels.
The ability to accurately map existing conditions provides a solid foundation for designing rehabilitation strategies. Engineers can assess structural integrity, identify areas prone to deterioration and plan repairs to extend the lifespan of tunnel assets.
Tunnels present a unique set of conditions—darkness, dampness, GNSS restrictions, traffic—that can impede effective infrastructure management and increase costs for rehabilitation.
The mobile mapping workflow provides a safer method upfront for collecting detailed asset data, while terrestrial tools support the backend construction work involved with expansion and upgrades.
Whether capturing data with terrestrial or mobile mapping solutions, there are hardware and software options available to achieve the required level of accuracy.
For one tunnel rehabilitation project in northern Norway, conventional total station technology was impeding survey crews’ ability to keep up with the daily excavation, blasting and bolting. To improve productivity, an efficient scanning total station was employed instead.
For this complex project that included widening the carriageway, adding new drainage systems and building new road surfaces, the combination of surveying and scanning technology was incredibly versatile, ranging from collecting a full-dome scan to establishing ground control to producing tunnel profiles to calculate excavation volumes.
Applications in Tunnel Rehabilitation
- As-Built Documentation: Accurate as-built documentation is essential for rehabilitation projects. Mobile mapping captures precise measurements and configurations, enabling engineers to design retrofit solutions that seamlessly integrate with existing structures.
- Monitoring Construction Progress: During rehabilitation, scanning facilitates real-time monitoring of progress and quality assurance. It allows project managers to verify that construction aligns with design specifications and identify potential issues early, thereby minimizing delays and cost overruns.
- Safety and Risk Mitigation: By identifying structural weaknesses or hazards promptly, mobile mapping enhances safety for construction crews and maintenance personnel. Real-time data updates ensure that all stakeholders are informed of evolving conditions within the tunnel environment.
The Future of Reality Capture
Looking ahead, advances in reality capture technology hold promise for further improvements in tunnel asset management, while machine learning and artificial intelligence (AI) algorithms are increasingly integrated into data processing workflows, offering predictive analytics capabilities that anticipate maintenance needs and optimize asset performance over time.
As workflows continue to develop, the industry's ability to harness the full potential of mobile mapping will only grow stronger. Collaboration between technology developers, engineering firms and infrastructure owners will be pivotal in refining these technologies and expanding their applications to meet the evolving demands of tunnel infrastructure worldwide.
Mobile mapping stands at the forefront of innovation in tunnel asset management, enabling unparalleled efficiency, accuracy and safety across all stages of a tunnel's lifecycle. Embracing these technologies today positions stakeholders to not only meet current challenges but also to lead the way towards a more sustainable and resilient infrastructure landscape tomorrow. RB
Karl Bradshaw is a market manager for mobile mapping at Trimble.
