Dig Diary: Aerial Archaeology
by Bryan Haley
I get to do some pretty interesting and exciting tasks as part of my job. At the top of the list has to be aerial archaeology, which consists of taking various types of images from way above a site. This aerial perspective allows the archaeologist to better view the full context of patterning that is on the ground. In some cases, like geophysics, it can be used to detect buried archaeological features as soil or crop marks.
There are many platforms that can be used to achieve this aerial perspective, including balloons, remote controlled airplanes, manned airplanes, helicopters and even satellites in orbit miles above the Earth. Another vehicle that can be used is a powered parachute, which is sort of a combination of a dune buggy, an airplane propeller, and, of course, a parachute.
There are many types of images that can be taken from the air. The most basic of these are simple film or digital cameras that capture black and white or color pictures. More advanced systems can capture images that go beyond what the human eye can normally see, such as thermal infrared. A thermal infrared camera "sees" differences in heat, which can be helpful because, in some cases, buried archaeological features can cause these variations.
I flew over New Philadelphia a couple of weeks before the Time Team America shoot in a two person powered parachute. While the pilot controlled the aircraft from the front, I sat in the back collecting images with a thermal infrared camera.
The tricky part about using the powered parachute was finding the right weather conditions to allow us to fly safely. Flying in winds less than about 12 miles per hour helps ensure that the aircraft is not blown sideways during takeoff or landing. The lightest winds are usually in the morning or in the evening and so these are the best times to try to fly.
Once I had some images I liked, I analyzed the data on my laptop. Coordinates were assigned to the images so that they could be referenced to exact locations on the ground. At the time we flew over the site, it was covered in thick grass, which can obscure the buried archaeology. Nevertheless, we were able to identify a subtle heat pattern that could be related to historic activity at the site. The aerial results were compared to the geophysical results and historic maps to help decide where to dig.
You can see an example of the infrared images we collected in the Incident Room.