Archaeologist breaks old ground in new ways with GPR technology

Hans-Dieter Bader is an archaeologist with 30 years’ field experience. Originally from Germany, where he completed his training, Dr Bader has worked in New Zealand for more than 20 years with occasional projects taking him across the pond to Australia.

Dr Bader specialises in geophysical mapping of archaeology sites, having purchased his own geophysical survey equipment 12 years ago.

“I believe I am the only contracting archaeologist to own this technology,” he said, adding, “I normally use a Fluxgate gradiometer to map what lies beneath the surface of the earth. In the past I have also used soil resistivity and soil conductivity.”

Recently, Dr Bader’s work has focussed on locating ancient Maori gardens in Auckland, dating between 200 and 600 years old. The project involved working in a volcanic field and Mr Bader found that to get more comprehensive results, he needed to complement his geophysical survey equipment with ground penetrating radar (GPR).

“The magnetic response from the geology of the site made getting reliable results with the geomagnetic technology a challenge,” he said. “To catch the drawback I hired a US Radar Q5C GPR from Position Partners New Zealand to help fill in the gaps and get a complete picture of the area.”

Dr Bader is thought to be the first archaeologist in New Zealand to deploy both geomagnetic methods and GPR together on the one site.

To identify the Maori garden sites, Dr Bader looks for fine grade changes in the soil layers. “In normal terrain you would expect to see topsoil and subsoil beneath it, whereas in Maori garden locations there is a middle layer of planting soil,” he said. 

“The GPR shows exactly where these differences in soil layers are to help me identify the gardens accurately. The radar also picked up areas near to the gardens where Maori people made pits to store kumara underground.”

Although Dr Bader has had some experience with GPR technology in the past, he found the US Radar system particularly user friendly. “I would say it is the ideal solution for a novice or occasional user, it is extremely easy to operate and it also delivers very accurate results,” he said.

“It is fully self-calibrating and you see live results on the screen as you go, which makes it easy to know that you are capturing everything you need,” he added. “I also liked the fact that I didn’t have to use any additional software, I could simply save the data as a JPEG file without having to export and import between platforms. The file is then displayed in its geo-rectified position in GIS software and can be compared to the elevation model of the landscape and other geophysical survey results.”

When researching which GPR would best suit his needs, Dr Bader explained it was a simple decision: “All of the suppliers in New Zealand only hired their systems with an operator, which was firstly not what I needed and secondly, too expensive.”

Through Auckland-based Optical Services, which has an alliance agreement with Position Partners, an Australian company with a branch in Christchurch, Dr Bader discovered he could hire just what he needed.

“I knew that Optical Services offered a wide range of survey equipment, but I only recently discovered its partnership with Position Partners, which offers a broader range of geospatial solutions,” he said.

“I have to say the process was a dream from start to finish – I simply picked up and dropped off the GPR from Optical Services here in Auckland, and the system worked perfectly to give me the results I needed. Overall the setup was very efficient and well organised.”

Dr Bader is pleased with the results he has achieved using both geomagnetic methods and GPR. “Combining the two technologies and layering the data has given me very accurate results,” he said. “Working in areas that have been occupied for such a long time is challenging, however these methods have enabled me to identify the Maori garden sites with relative ease.”