Aerial photography

The view from above
Archaeologists use aerial photography all the time because the pictures taken from aircraft can highlight archaeological features that can't be seen on the ground. If there are walls or ditches under the surface, for example, these can affect how plants grow.

This is because ditch fills hold more water than the surrounding landscape, and so in the summer, when the ground becomes dry and parched, the routes of ditches appear a darker green where the grass above them is still supplied with water to grow. In the case of walls lying under the surface, grass growing above them can become parched more quickly than in the surrounding area, so they show up as lighter lines on the surface.

Though much of Britain has now been photographed from the air, this isn't always what archaeologists require. If a particular area they are interested in hasn't been recorded from the ideal angle, during the most suitable season or in the best light (the angle of sunlight and shadows can make a dramatic difference to which features show up), it may be desirable to charter a special flight. Of course this is expensive and the money is not usually available.

Radio-controlled helicopter
At Cranborne Chase, Time Team tried out a new system to get close-up aerial photography of the trenches and surrounding landscape in a quick and financially viable way: This was done by Julian Cox and his radio-controlled helicopter from Autography Aerials.

This electrically powered model is much quieter and cleaner than the petrol-engine versions that modellers use. Mounted under the helicopter is a Sony DSCV1 five-megapixel digital camera to take the high-quality images. 'At the moment we can stay in the air for about five minutes carrying all the equipment,' says Julian. 'That's plenty of time to get up to 400 feet and into position to take a whole load of great photographs.'

Live feed
The clever bit is in getting the camera into position to compose the photograph. 'The viewfinder from the camera is connected to a neat video link,' Julian explains. 'This transmits what the camera can see to a video receiver attached to the standard radio controller that I use to fly the craft. The receiver is then connected to a special "head-up display" (HUD) attached to my glasses, so that I get a direct live feed from whatever the camera can see. The results, I'm sure you'll agree, look excellent.'

With a mains transformer fitted in his car, Julian can set up the helicopter in five minutes, fly and photograph, download the images and burn a CD all in under half an hour. 'This is great,' says landscape archaeologist Stewart Ainsworth. 'We can send it up and be looking at the results on site in no time.'

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