What is Lidar?
Lidar stands for Light Detection and Ranging. It is a remote sensing technique which allows a very detailed digital model of entire landscapes to be constructed. A pulsed infra-red laser beam is scanned from side to side from an aerial platform (usually a plane or helicopter) as it travels over the terrain, sending thousands of infra-red laser pulses to the ground every second. These pulses reflect off the ground and are received by detectors on the plane, which calculate the distance between the plane and the ground. By flying back and forth, it is possible to gather millions of these measurements – the New Forest Lidar Pilot Survey captured over 60 million – which are exceptionally accurate. These can then be stitched together to form a surface which is an accurate model of the landscape.
Traditional archaeological survey is often difficult in woodland as vegetation makes sites difficult to reach, to see, and to record. This makes the ability for lidar to ‘see through’ vegetation one of its main strengths. Because the laser pulses can filter through the leaves and branches of trees, we are able to strip away the vegetation and look at the ground, and the archaeology, beneath, often with spectacular results.
We can also digitally manipulate the lidar to produce different images, by illuminating the model in different ways, examining slope and aspect, viewing in 3D and drawing sections across the landscape. We can also combine the lidar with other information, such as historic mapping dating back to the 18th century, aerial photography and records of known archaeological sites. All of these techniques help us to accurately identify and interpret sites, which can then be checked on the ground. More information on the use of lidar in the New Forest and further afield can be found in the documents below.
Related documents
Past landscapes beneath the trees using Lidar in woodlands - September 2010 morning (4.5 MB)
Past landscapes beneath the trees using Lidar in woodlands - September 2010 afternoon (6.1 MB)
Past landscapes beneath the trees using Lidar in Woodlands
