On our second day on site I continued to laser scan the Iron Age structures to the south east of the archaeological site of Jarlshof. Here, there is a mix of buildings and features dating to different times, all seen at once. Archaeologists refer to such mixes as palimpsests. In this area of the site, the broch, which dates to the Middle Iron Age in the north Atlantic, is the central focal feature. I used the University of Bradford Visualising Heritage group’s FARO X330 laser scanner to survey inside the intramural gallery between the broch walls as it’s nice and portable, using our sturdy but sleek carbon tripod. A bigger scanner and tripod wouldn’t fit in such a small space! It was helpful to have experience of surveying and processing point cloud data of such galleries from the Broch of Mousa last year, as I had a good idea of how close together the scans needed to be to get good coverage all the way around. HES’s tiny “milking stool” tripod was also handy to perch the scanner in the little drystone window at the end of this passage.

During the Late Iron Age extramural buildings were constructed around the broch. Some even directly made use of the sturdy walls of the broch itself to build onto. The most famous and impressive of these are the wheelhouses, so named as the shape of these buildings in plan view is like a wheel, with radial piers jutting into the central area like the spokes of a wheel. James surveyed the wheelhouse with an intriguing medial wall that sits to the west of the broch, whilst I tackled the building to the east. Sofia and Alan used the Leica P40 scanner to survey the Norse longhouses at a long range, while the rest of the team scanned another site in the care of HES – the Ness of Burgi, just across the sea from Jarlshof on a little peninsula! Our radios could reach each other!

It was nice to see so many visitors interested in our work and my research and I’m always happy to tell people more – and direct them to this blog of course 😉

You can tell a laser scan survey is happening as you’ll often spot many large yellow tripods standing up around a site – these are our heavy duty ones that are sturdy and can face most extreme weather conditions! Sometimes these have black and white checkerboard targets mounted on them, or the laser scanners themselves, which you’ll notice rotating around. We use smaller, lighter tripods too, as I did today (see main photo), when the ground conditions are safe enough to do so and in confined spaces. Some of our scanners, like the FARO X330, beep while they’re scanning, so you know it’s doing it’s job, though they stay silent when taking photos!

If you see a scanner on it’s own without an operator, it’ll most likely be recording its surroundings. This is because the surveyor doesn’t want to be in the way of the scan – we’re trying to record all of the amazing archaeology, not ourselves, after all! Because of this, it can really help the surveyor if visitors do not approach a scanner while it’s on it’s lonesome (like in the above photo), so they don’t accidentally get caught in a scan or get photographed by the scanner!

It’s fantastic if they can be helpful by exploring a different part of the site while the scanner’s there. Scans are usually done in 15 minutes and we move the scanner to a new position after that, so there’s time for visitors to return to the part of a site they missed. It’s also important to never touch or be too close to our equipment for safety reasons (scanners and tripods are heavy!) and for accuracy of our data capture! Even a teeny nudge can cause massive problems for us in processing the data, which can take many hours to fix, so understanding this is massively appreciated by surveyors. We had some wonderfully understanding visitors today. I hope the above info is useful to those who are new to laser scan surveys, and a massive thanks to you all for making our jobs a bit easier! 😀