LiDAR, standing for "Light Distance and Ranging," also known as Airborne Laser Scanning (ALS), is a survey technique that has been used by archaeologists for just under 20 years now. It has aided in the discovery of new sites, and is particularly important for its ability to show archaeology beneath vegetation.
The technique works using a plane-mounted laser scanner which sends out millions of pulses of light towards the ground and detects the reflections. From this data a highly accurate “point cloud” is created of everything the light has hit on the earth’s surface. The points are then ‘classified’ for whether they are vegetation, buildings, or the ground surface; all of the above-ground points are filtered away, leaving us with a "digital terrain model" of the bare earth, which allows us to start to detect archaeology!
We have commissioned a bespoke survey of the Chilterns and some surrounding areas. At 1400 km2, it will be the largest LiDAR survey ever flown for archaeology in this country, and one of the largest in the world. The survey will be taking place over the winter of 2018/19, with the data becoming available in late spring 2019.
You may know that the Environment Agency has begun a program of surveys over the whole country, and their data is freely available for use, but a bespoke survey was settled on for this project for two main reasons: firstly, the Chilterns has not been a priority for survey by the EA as their main concern is flood risk, and the permeable chalk of the Chilterns generally has low risk of flooding; secondly, we have commissioned a very high resolution survey (25 cm resolution, as opposed to the 1 m resolution of most of the EA survey) which means we will be able to pick out far more detail, and therefore many more archaeological features from the survey, particularly under tree cover.
Once we have the data from our contractors we will then be producing a number of different ‘visualisations’ of the data, in order to make the humps and bumps show up clearly. Come May 2019, members of the public will be able to log on to our mapping portal and trace into our database any and all features that they can see, from barrows to possibly even new hillforts!
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