Seeing The Forest

The old saying about not seeing the forest for the trees comes to mind when reading this story from the Sunday Times. Scientists in Britain are using lidar to see through the forest entirely and discover the terrain beneath. That includes all the archaeological sites that have been hidden by the trees. Lidar, which works in much the same way as radar except that it bounces a laser beam off the target, can strip away the interfering vegetation and let researchers clearly see what is underneath.

Hundreds of archaeological relics are being uncovered by a laser reading technique that can see through trees to reveal the landscape hidden by forests.

Trees and undergrowth are stripped away by the aerial detection system to show the remains of structures. Among the features uncovered by the system are a missing section of Offa’s Dyke, a Roman road and suspected Iron Age field networks.

The technology, called lidar, bounces laser beams off the ground from an aircraft 3,300ft (1,005m) above and records the minute differences in time it takes for the light to return to build up a three-dimensional picture of the landscape beneath the trees.

The system uses specially designed computer software to distinguish between the laser light bouncing off leaves and the light bouncing back from the ground. The technology dates back to the 1960s but it is only in the past five years that it has been sufficiently well developed to allow archaeologists to start mapping land covered by forests.

It is expected to reveal thousands of previously unknown or unmapped ancient settlements, fortifications, farms and features in Britain over the next decade. Lidar is a laser version of radar, and was tried out at Welshbury in the Forest of Dean, Gloucestershire, where an Iron Age hill fort was known to be hidden by trees. With the trees stripped away by lidar, the embankments of the hill fort were clearly defined.

That's kind of a neat application. Here are a couple of the images derived from the technology at the English Heritage website. It includes links to others involved in the research.