LiDAR
Perhaps one of the most exciting historic heritage projects that the QLPS is undertaking is a LiDAR survey of the entire LPS area as part of our ’Understanding the Landscape’ project. Following specialist training provided for us by Historic England, the results of the survey are now being analysed by a group of volunteers.
LiDAR (Light Detection and Ranging) is a remote sensing technique which uses laser scanners, mounted on an aircraft, to produce high-resolution landscape surveys. The scanners emit many hundreds of pulses per second and measure how long it takes the reflections of these pulses to return. These measurements are then processed, to provide accurate measurements of the ground surface which are in turn used to create detailed 3D maps known as Digital Terrain Models.
The great advantage of LiDAR data to archaeological work is that, unlike conventional aerial or satellite imagery, LiDAR data can be processed in various ways. For example, simulated light can be cast across the digital landscape to create shadow effects from various directions. These ‘hillshades’ can help to reveal archaeological earthworks which may be indiscernible on the ground or to aerial photography. Perhaps most excitingly, LiDAR allows the effective ‘removal’ of tree cover, allowing us the potential to identify archaeological sites and features previously hidden beneath the canopy, as well as helping to more fully understand existing ones.
The Quantock LiDAR Survey was being undertaken by Bluesky International who have great experience generating LiDAR surveys for many archaeological and heritage projects with clients including The National Trust, Peak District National Park Authority, Kent Downs National Landscape, and the Forestry Commission. The archaeological visualisations of Bluesky’s data were prepared for us by ArcHeritage, part of the York Archaeological Trust.
A previous LiDAR survey undertaken by Bluesky of locations on the Blackdown Hills as part of Historic England’s National Mapping Programme, revealed amongst other things, a ‘lost’ Neolithic interior causeway at Hembury Hillfort; new features at Dunkeswell Abbey and the presence of small motte and bailey castles at Buckerell and Bushy Knap. LiDAR’s ability to reveal subtle earthwork features also helped greatly increase understanding of the influence of medieval and post-medieval farming and industry on the landscape character of the Blackdown Hills.
The Quantock survey was conducted at a higher resolution than the Blackdowns survey (25cm rather than 50cm) and had an immediate impact. Arriving just prior to our excavations at Cothelstone Hill, the LiDAR clearly showed that the ‘linear’ earthwork we were preparing to investigate, was in fact a sub-circular enclosure. The subsequent excavations have shown this to be of Late Bronze Age date, making it unique amongst the archaeological features of the Quantocks.
Our volunteers have already identified almost 1,400 previously unidentified archaeological features including charcoal burning platforms, ancient field boundaries and even some previously unknown prehistoric burial mounds. The next stage will be to head out onto the hills to ‘ground-truth’ some of these features before they are added to the Somerset Historic Environment Record, which records the known historic environment across the county.