What is out of sight is not necessarily out of mind. Unknown underground voids and cavities have provided problems in many civil engineering projects. In these situations Inspectahire has carried out underground surveys using CCTV and laser scanning systems to understand the problem.

Visual inspections of a void are achieved by deploying a waterproof CCTV camera down a borehole. Live video images of the inspection site are then relayed back above ground. The size and shape of the void is then measured by deploying the Cavity Auto scanning Laser System (C-ALS), a ruggedised 3D laser scanning device, down the borehole.

The C-ALS probe has a diameter of 50mm and is deployed by cable. It features a self-navigating, motorised two-axis scanning head that provides a 360º scan of the entire void and has a range of up to 300m down hole. A 3D model of the void and its dimensions is then created in minutes. C-ALS can be encased in fibreglass rods for up hole inspections to a length of 150m.

By using the two systems in tandem, a greater understanding of the void can be achieved. The data also provides a benchmark for engineers to monitor the void over time.