Aerial lidar mapping uncovers prehistoric archaeological sites

Lidar (light and radar) uses laser precision to sense the surrounding environment. Laser beams are emitted and the amount of time taken for them to be reflected from objects and return to the sensor is measured. This provides the distances from various objects and allows a three-dimensional map of the environment to be built up quickly.

The technology was applied to the National Trust’s Wallington 13-hectare estate in Northumberland as it prepares to decide where to plant 75,000 British native trees as part of ambitions to plant 20 million trees by 2030 in order to help tackle the climate crisis.

The lidar-created map found evidence of archaeological sites dating from 2000BC to 1900AD, including traces of historic, healthy woodlands dating from the mid-eighteenth century which were cleared and not replanted.

Other findings include the discovery of early farming systems which were cast aside in the 18th century by the previous owner of the estate and at least half a dozen different forms of ‘ridge and furrow’ cultivation.

Previously recognised Iron Age camps, like mini-hillforts, estimated as dating from the centuries immediately prior to the Roman invasion, have been surveyed with greater precision to reveal more eroded outlying features; possible annexes to the main enclosures; linear features potentially of adjoining fields or enclosures, and even suspected prehistoric pathways.

Other discoveries include numerous squarer features of a similar type believed to date from Roman times and previously unknown landmarks, including a 17th-century recreational landscape.

National Trust archaeological consultant Mark Newman said: “This is an exciting moment in the 5,000-year history of this special estate. The lidar findings have shone a light on much more than we could have imagined so that we can better understand the history of the landscape to help inform plans for its future.

“All of these discoveries will be investigated further to ensure none are impacted by the upcoming planting plans and to preserve their archaeology for future study. Embracing, valuing, understanding and respecting the cultural landscape is completely complementary to planting for the benefit of the natural environment we must achieve, through planting projects like this, in our fight against the climate crisis. 

“We can now plant with confidence, selecting areas for planting that avoid damaging any significant archaeological remains. But - and this is one of the things we are really excited about - we can now actually recreate areas of lost historic planting which we didn’t previously know about.

“It makes sense to mirror history. These areas should deliver even more habitat benefit than was originally intended and once again contribute to the picturesque qualities of the landscape while also restoring lost features of the historic environment."

Additional fieldwork to record the landscape will be carried out before planting begins in November to complement the lidar remote sensing.

In 2018, researchers used the lidar technique in Guatemala to uncover more than 60,000 previously unknown Mayan structures.

Last year, during lockdown, archaeologists from the University of Exeter were able to identify new medieval and Roman sites across the south-west of England while working from home by analysing data from lidar scans.