What is it?
How Lidar works
Interpreting the ‘lumps and bumps’ on the landscape can tell us a lot about how the New Forest has been used and exploited since the Neolithic period.
Finding and recording archaeological features through traditional field survey can be difficult and time-consuming for archaeologists: using such techniques it is estimated that it might be more than 100 years before we have an understanding of the number and range of sites.
Airborne Lidar (Light Detection and Ranging) makes it possible to speed up the process. It is a remote sensing technique that allows a very detailed digital surface model of entire landscapes to be constructed.
A pulsed laser beam is scanned from side to side from a plane as it travels over the terrain, recording thousands of three dimensional points 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 using the known speed of light coupled with the accurate positioning of the plane.
It is possible to gather millions of these exceptionally accurate measurements that can then be processed to create a surface that is an accurate model of the landscape.
How Lidar helps
Traditional archaeological survey is often difficult in woodland as vegetation makes sites impossible to reach, see and record. Lidar’s ability to ‘see through’ vegetation is one of its main strengths.
Because the laser pulses can filter between the leaves and branches of trees, we are able to strip away the vegetation and look at the ground – and the archaeology beneath the tree canopy – often with spectacular results.
We can also digitally manipulate the Lidar to produce a range of 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, near infrared imagery 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.
Lidar and the Higher Level Stewardship scheme
The Lidar project is funded as part of the New Forest Higher Level Stewardship scheme. One of the aims of the HLS scheme is to encourage responsible land management that will help to preserve and enhance the environment, including the archaeology within it.
Lidar is an incredibly powerful tool in helping to manage the Forest landscape and identify archaeological sites.