3d Laser Tunnel survey; wet and dry
Laser scanning methods have been in use for several years to survey objects, buildings and tunnels and the level of detail that can be obtained is stunning. It allows for wide range of inspections to be completed including, mapping, surface condition assessments, over and under breaking analysis, component inspection and relationship to surface features or activity. There are two approaches: a handheld laser unit or SLAM (Simultaneous Localisation And Mapping), or terrestrial LIDAR (Light Detection And Ranging) unit; both have their advantages. A hand-held SLAM is rapid and will go places that a LiDAR unit cannot, so is preferable in long or small tunnels, but it cannot capture the detail that a LiDAR unit can, which is a slower more considered approach. Commendium will use the most appropriate method for any job and typically uses a blend of technologies to gain the desire output.
With partners, The Water-Services Group, we are able to offer a multi-technological approach to surveying tunnels, aqueducts or aquifers. Uniquely, with software built in-house, we are able to combine and synchronise SLAM, LiDAR, Ground Penetration, Sonar and Airborne survey data into complete 3D models of underground subjects, so that, for instance, we can create
- a geolocated map of a tunnel,
- accurately assess the depth below ground of a tunnel at any point on the surface,
- accurately measure spatial relationships between underground features and
- give a detailed, even forensic, 3D condition survey,
- a full 3d laser tunnel survey
all in dry and partially or fully flooded systems.
We can survey where humans cannot venture using robotic vehicles, but also have the necessary confined space, access, and safety training to physically venture into these tunnels.
We have recently been testing these combined technologies in Speedwell caverns in Derbyshire. Here a stairway leads to a boat ride along 450m of half-flooded tunnel, meticulously mined out in the 1770s, to a large chamber. We where able to combine sonar data from underwater, SLAM data long the tunnel and high quality LiDAR data in the chamber at the end, into a single 3D dataset.