Heaning Wood Bone Cave in West Cumbria is a prehistoric burial cave with a long history of research. Ian Smith has recently shown that the human bone from the site was Early Bronze Age while the large assemblage of different species of animal remains were Early Neolithic.
Cave explorers in the mid 20th century got into the Cave this way through an extremely tight squeeze further along this horizontal passage but, by the time Ian was carrying out his research, improvements in the average British diet meant that no one was capable of entering the cave that way.
This was probably the prehistoric entrance to the cave. It was discovered in the 1970s by the landowner and has been cleared and explored by Martin Stables. This shows that the cave was more of a vertical shaft than previous suspected, which fits well with the pattern I identified in my upcoming book for Late Neolithic and Early Bronze Age cave burials to be in vertical shafts like this. I have been helping Martin with the survey and recording of the cave. As you can imagine, producing a measured drawing of a constricted and irregular shape like a cave can be quite challenging. In the past I have used a total station to do this kind of thing, which involves a lot of time underground but is relatively quick on the computer afterwards.
For more on site speed and accuracy of survey I did the Heaning Wood survey with our Faro Focus laser scanner. This shot shows the machine set up at the choke point in the vertical shaft where most of the human and animal bone built up. Behind the tripod you can see the shaft heading off down into the bowels of the earth. This also gives a good sense of how tight the space is, this was taken from the ladder on the way back up the entrance shaft. The scanner works by bouncing its laser off the cave wall and logging the position of many millions of points to build up a 3d model of the cave. To do this it has to spend about 30 minutes spinning around on the tripod and while it is doing this you can’t be in sight of the scanner (otherwise a ghostly blurred image of the surveyor turns up in the final computer model). When you set the machine off it gives you about 30 seconds to get out of range, this is fine if you are scanning a room (we also use this scanner in crime scenes) but scrambling out through a narrow vertical tube in this time is more of a challenge.
Even so, the survey is the easy part. I did three overlapping scans of the cave interior to cover any blank spots. Clare and I then spent about three hours in the imaging lab trying to make sense of the data. When you get the numbers out of the scanner these different scans have to be registered and linked together to create the 3d model of the cave. This is what the raw scan data looks like. Within the two scans on screen here you can see various control objects that I added into the cave to help the scanner link the different scans together. These include white plastic globes and checkerboard patterns. The software compares the measured distances between these points to build up a grid of similar distances. This view shows how Clare and I made sure that the software was linking the right control points together. It normally does this automatically but some times, and this was one of them, its gets confused. The issue this time was that two of the globes were close together and only one showed in each scan. The software decided they were the same point but, of course, they weren’t.
Once this little issue was fixed these two scans snapped together nicely. This view shows the merged model with the first scan highlighted to show which bits of data came from where. We are now at the stage where we have a nice 3d model of the main bit of the cave we can rotate and examine.
This view shows the width of the chamber quite nicely, while also giving a sense of the depth of the vertical shaft.
On the other hand, this view clearly shows up the depth of the deep fissure beyond the point where most of the bone was found. This really shows well how a 3d scan like this can give you a much more nuanced understanding of a cave than even the most accurate plan.
Rick
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