Rock faces and RPAS

In early 2019 I took my ANAFI flying camera up to Mt Coree, aiming to capture some of the incredible sunsets that can be seen there. I also spent a battery flying a very close range survey of a cliff face, collecting images manually to create a very high resolution model. My aim was to measure the climbing anchor bolts – which is pretty ambitious. Here’s a photo of one – it’s about 6 x 3 cm in area, and sticks about 3cm out of the cliff. It is secured by a 10mm bolt, glued into the rock.

Anchor bolt number 7 – Wind Wall, Mt Coree

For this job, an automated and top-down flight pattern would have been very sub-optimal. To keep detail across the whole cliff, I flew vertically up and down a few metres out from the rock face, clicking away to collect images.

If I did the same job again now it would be made vastly easier by Parrot’s recently-added GPS lapse photography mode. This automatically fires the camera at set distances from last image position in three dimensional space, letting the pilot focus on not crashing! At the time, however, it was all done by hand.

The results are pretty good. Using some klunky Javascripting I made this little report, integrating a 3D point cloud viewer, images of the bolt anchors, and even a fly-up video! You can also click for a full screen view.

…and was the aim – measuring bolts – achieved? Almost – try to find them in the point cloud view and see if you can size them up. To do this for ‘real’ I’d spend at least another battery and double (or triple) the number of images collected. This was made from only 140 photographs!

Underlying data are stored as Entwine Point Tiles (EPT) – meaning I can directly query this dataset for analytical tasks using PDAL. Given that this survey was flown without ground control, a future exercise might be working out how to align this super-dense data with older, less dense surveys.

For now, it’s a neat proof of tricky data collection with a very small RPA – and generating a nifty interactive-but-static report that you can keep going back to as long as you have an operational web server.

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