What is tunnel scanning?
In the past, tunnel inspection and documentation was a “camera and clipboard” manual process to document geology, tunnel lining conditions, or assets within tunnel networks. It was time-consuming and inconsistent in terms of objectivity, continuity and spatial context.
Today, we combine light detection and ranging (LiDAR), high-resolution image systems and photogrammetric processing to derive a complete geometrical and visual depiction of a tunnel surface at a chosen point in time.
How tunnel scanning works
With a variety of fixed and mobile platforms, Land Surveys combines laser scanners and high-resolution cameras to rapidly record the tunnel surface to a resolution of up to 1mm x 1mm. Mobile systems can capture data at ambient traffic speed, reducing what used to take weeks and months, to just hours.
From this data we then generate highly precise true-colour, textured 3D models of the scanned tunnel surface.
Utilising tunnel scanning
The central purpose of tunnel-scanning systems is to create a continuous 3D reconstruction of tunnel surfaces in the form of textured 3D data. This data can be used for a range of construction, documentation and inspection purposes, including:
- tunnel construction; geological mapping;
- as-built/evidence of status;
- asset management/maintenance; and
- change detection.
The benefits of using tunnel scanning
Speed of data capture (up to 80km per hour) translates into minimal tunnel closures, traffic control and time spent by personnel in the tunnel environment. Inspecting a tunnel’s condition or mapping defects and assets can now be undertaken in a virtual 3D environment, with sub-millimetre resolution of the tunnel’s surface enabling exceptional visual detail of its surface condition.
Detection, mapping and measurement of tunnel components can be undertaken in a centralised structured database, managing inspection intervals and temporal changes from a single point of truth.
Land Surveys can help solve challenges with tunnel scanning
Digital analysis of the tunnel surface allows greater detail to be captured than previously possible, thereby increasing the overall quality of the data harvested and enabling accurate recording and mapping of the following survey elements:
- components (blocks, niches);
- asset installations (lamps, traffic control systems et cetera)
- damage and defects (cracks, spalling, efflorescence);
- asset condition;
- geometrical shape;
- excavation profile check; and
- geological structures.
These features are identified and mapped in the 3D virtual environment, and can then be linked to existing databases, previous records, external documents, or work program protocols.
By overlaying tunnel scans generated from different periods, changes in the tunnel surface can readily be detected and monitored over time. Spatial and temporal changes can be quantified (via 4D change detection) and serve as a basis for subsequent inspection and rehabilitation activities. And database elements and information from our inspection software can be exported in open data formats (LAS, OBJ, ASCII) and interfaced with a large number of CAD, GIS and BIM products.
Why choose Land Surveys for your tunnel scanning requirements?
By Land Surveys combining the latest measurement systems and powerful software, it can continue to innovate by implementing multi/hyperspectral sensors that can gather further data on the material properties – (concrete, steel and asphalt – of a tunnel.
Continued development of machine learning (ML) libraries by Land Surveys presents opportunities for fully automated crack and defect detection, as well as statistical analysis of tunnel ‘health’ and safety parameters over time.