One of the main challenges of this project was capturing 3D LiDAR data in a GPS-denied area. In a conventional mobile LiDAR application an IMU (inertial measurement unit) and a GPS antenna are used to accurately map each individual LiDAR point. Without the aid of GPS, our team had to look at other options. For this reason, we developed a system using a conventional terrestrial LiDAR scanner that can be calibrated to create a highly accurate 3D point cloud.

Minimizing Shadowing & Difficult to Reach Areas

Another challenge we encountered was the difficulty of capturing data in hard-to-access corners or behind existing equipment (transformers, switches, etc.) We determined that our LiDAR acquisition system needed to be small and versatile so that it could capture scans throughout the vault while minimizing shadowing in the images. We mounted our LiDAR system to a six-wheeled rover that could be operated above ground via First Person Video (FPV) to scan the underground vault.

Safety, Safety, Safety

The last, but most important piece of the puzzle, was deploying acquisition technology using safe techniques. The underground vaults were highly sensitive to disturbance and, if equipment malfunctioned, we would not be able to retrieve our scanner. We implemented various fail-safe mechanisms to allow quick retrieval of our rover if, for any reason, power, navigation, or video were lost. Further, our deployment techniques ensured that no personnel had to be in, or around, the manhole once it was opened.