Tunnel LiDAR Fun!


Lidar scanning underground requires extra care and attention to detail. The harsh environment, which is often wet and dusty, will challenge the limits of even the top scanners. As time is generally the most critical concern, phase-based scanners are optimal. With scanning rates of up to one million points per second, combined with a full hemispherical view, these scanners allow the job to be conducted quickly and accurately with minimal disruption to a construction schedule.


Another issue, of course, is knowing absolute rather than relative position. A scanner always knows where it is ‘relative to itself’ and, of course, multiple overlapping scans can be combined into one ‘scan word.’ But absolute positioning requires external coordinates. In a tunnel, the de facto method for position - survey grade GPS - isn’t available. Careful surveying of landmarks is the only viable approach for ‘far underground’ positions, though for a short tunnel calibrating successive scans to eventually link to an external frame of reference can work with limited accuracy.

Why Bother? Lidar scanning underground is commonly used for quality control, geological mapping, as-built models, and deformation analysis. As lidar scanning becomes more commonplace in the underground environment better workflow solutions and processing algorithms will be essential.

See the tunnel liar photos posted in Visualize for some examples!

The Rock Bench experience

Welcome to Rock Bench, the little idea that will hopefully grow!

You may notice that our first attempt at a host site is rather modest, in keeping with our general idea that what matters is the volume of data not the shiny hubcaps on the website. We’re hoping to move to a slightly more sophisticated CMS eventually, largely to allow user-generated and user-submitted content. For now this is pretty much a top down experience.

We welcome ideas on how to grow the site and how to improve the quality of the data and experience we offer, modest though it now is (and likely will remain!).

Matt, John, Rob, and George


This is what we’re about! Can we evaluate a rock mass using remote sensing? If so, how? Can we share great datasets so the community can validate tools?