Global Archaeology Expert: Ben Thorne

Taking survey points

The first Global Archaeology Expert to be featured hails from the North Island of New Zealand. Ben Thorne of Datum Archaeology is a Contract Archaeologist and Survey Specialist in spatial field recording. That means that he digitally records the artefact locations, features and topography of an archaeological site and turns that into maps and photo realistic models that can be used to better visualise how a site looked in the past. It is very important for archaeologists to have detailed maps of sites so the individual artefacts and features like houses or hearths can be understood in relation to each other and the wider landscape.

“Looking at the layout of features can help us to interpret activities on site over time, layout of structures, and the relationships between those structures. New Zealand sites, particularly Maori sites, have very defined spatial rules and patterns. Different areas are set aside for certain tasks and groups of people. Using site maps we can sometimes see these patterns. Looking at a plan of features can also aid in separating multiple phases of occupation.”

Taking survey points

Ben uses two complementary tools: a total station and a commercial surveying GPS unit. A normal handheld GPS – like those found in our phones – can be accurate up to about 4m, but the differential GPS (DGPS) that Ben uses corrects this 4m error using a known reference point. The known reference point can be inserted into his dataset after the recording has taken place to readjust the site map, or a real time kinematic (RTK) correction can be used during the recording process. The combined use of the DGPS with a RTK correction allows Ben to digitally map large areas for landscape contours, environmental features and archaeological features with a high degree of precision, as well as to set up control points (known locations on the New Zealand national grid) for his total station. The next step is to input his data sets into a Geographic Information System (GIS) software package that allows archaeologists to visualise and analyse all the data from a site in one package (e.g. soils, feature/context records, historic maps, etc.).

“The total station is used primarily for recording of archaeological features during excavations. While a GPS can also record features, once setup a total station is quicker, more accurate, and able to record more detail than the GPS.”

Flying a drone over a trench

Another method that Ben uses is photogrammetry – essentially making a map of points by overlapping a massive number of photographs. This process was invented in the mid 1800’s but today’s technology allows for millions of points to be taken and put into photogrammetry software to create a near photorealistic model. For ground recording Ben uses a high powered DSLR camera, but for larger work he has to send his equipment into the air.

“For the aerial work I have two drones/unmanned aerial vehicles (UAV’s). Both are custom made from Aeronavics BOT and AD airframes. The BOT UAV is lightweight with a limited lifting capacity but long flight time. I use this aircraft for landscape recording. The AD UAV is my heavy-lift aircraft. This can be fitted with almost any DSLR camera or a video camera. It has a much shorter flight time so is used for more detailed excavation photography.”

The future of this is virtual reality, something Ben has already been experimenting with. Already he can put the data he gathers using photogrammetry into virtual reality software and walk through excavations back in the office. The potential impacts of this type of work are fascinating.

A view from the trench – North Island

When Ben first started surveying during his university days his training involved using alidades and plane tables before he moved on to total stations. The first total stations he worked with were pretty basic – two person teams were needed and points had to be recorded individually. These days he uses a robotic total station that allows him to work independently and conduct automatic point recording while simultaneously recording DGPS in real time. He says that the biggest technological change he’s noticed over his career is the increase in the number of points that can now be recorded. When he began he averaged 6-10 points per archaeological feature, today he averages 20-40 points per feature. That is a huge leap in mapping accuracy, especially when you consider the increased precision in GPS positioning now available.

A North Island landscape

The technology that Ben is using is so cutting edge that it is difficult to find online literature on its pros and cons. When I asked him if there were any websites that discussed his type of archaeological work he could not find any articles that looked critically at multiple methodologies. Using drones for general site recording and photogrammetry is one of the ‘next big things’ in archaeology and archaeologists who are using this technology in the field are still sometimes having to rely on trial and error. Even Ben himself had to problem solve with the technology recently when he was recording a site where his drone wasn’t safe to use but the photogrammetry still needed to be done. As is usually the case with archaeologists a low tech solution was found for a high-tech problem: strap the camera to a 3m long painting pole. According to Ben the process took longer than using the drone (and I’m guessing was less fun) but had good quality results.

Taking survey points

Creating maps and visualisations of what archaeological sites look like now and what they looked like in the past helps archaeologists communicate what they have found to the public. It is this aspect of being an archaeologist that Ben considers to be the most enjoyable part of his work. Humans have not occupied New Zealand for very long – relatively speaking on a global scale – and so it is possible to sometimes link sites and the artefacts found on them to living descendants in both the Maori and European communities. It isn’t always possible for people to visit archaeological sites but the sites can be brought to them through the work that Ben does. Communication with stakeholders in the present is a major aspect of being an archaeologist in New Zealand and virtual reality and digital visualisations of archaeological sites help tremendously in explaining what was uncovered and how it was interpreted by the archaeologists. In New Zealand communication is shared between archaeologists and stakeholders.

“For Maori sites we frequently have local Maori working with us as monitors who report back to the hapu’s Marae […] When we are working with Hapu monitors it is really great to be able to talk through what we are finding with them. Their views and understanding of their own history can provide information that we can not get from the archaeological record alone.”

This is truly an insight into how the most cutting edge technology can be combined with the timeless practice of oral history to give us all a better understanding of the past. Ben’s work gives us insights into the archaeological record that were not possible even a few decades ago. Our awareness and appreciation of the past can only become more comprehensive as the technology advances and discussions between stakeholders continue to be fostered.

*** Thanks so much to Ben Thorne for agreeing to be featured as a Global Archaeology Expert and sharing his perspective on archaeology!

A drone
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