Last year I experimented with some photogrammetry in the confines of the Daren Cilau entrance crawl, the section known as the vice to be more specific, details can be found here:
Spurred on by the success in this short bit of passage I convinced myself that it would be a worthwhile project to try and accurately model the entire crawl from the surface to the final rescue box. One could simply video the entire crawl in single trip and use the video to produce a model but it is important to me to make this model accurate and to do this it needs to be surveyed so that the resulting model and can aligned to the survey data. For assessment of accuracy I surveyed both in and out so the loop closure could be examined and any poor data identified and sorted. To make this task more manageable I have broken the cave up into sections between the rescue boxes, these also make handy survey markers that aren’t likely to change location in between trips.
To date I have completed three trips; a trip consists of caving to the rescue box at the far end of the section with a small bag, surveying out from the box to the previous one then surveying back in. Caving slowly out with the Gopro and light trying to get steady footage before turning at the previous box and filming back in to the starting point. I then pack up the gear and cave back out. This involves lots of awkward caving for those familiar with the cave.
The first two of the trips have been successful and a decent model has been created from the surface (box 0) to box 2. On the third trip I found that my Gopro had been switched on prematurely and battery warning was already on before I started but this wasn’t discovered until after complementing the survey so I had a rather rushed trip filming back from box 3 to box 2 before the battery ran out. After some failed attempts at saving the data from the third trip this means I will have to repeat it as I was moving too fast for the image alignment to be successful.
The distances between boxes is as follows:
Box 0 to Box 1: 79 m
Box 1 to Box 2: 41 m
Box 2 to Box 3: 51 m
Pictures, model and videos to follow……………..