Ancient and modern: Combining different remote sensing techniques to interpret historic landscapes

A recent archaeological landscape survey project, undertaken as part of the English Heritage National Mapping Programme (NMP) looked at the relative value of using newly commissioned lidar data and pre-existing aerial photographic archives. The Savernake Forest NMP project covered 54 sq km near Marlborough in southern England and was mapped using both lidar and standard aerial photography and the results compared. As expected, the lidar revealed a lot of features not previously recorded within the forest, but systematic and careful analysis of all the aerial photographs showed that a number of features “discovered” by lidar had in fact been visible on photographs for 20, 30 and in some cases over 70 years! Furthermore, because the forest had been an important military site during the Second World War there were features visible on the wartime photographs that have left no physical trace and were hence not picked up from the lidar, but which help to explain surviving features and are vital to understanding the full history of the area. The survey showed that whilst various techniques will reveal certain features, to get a full understanding of a landscape you need to take advantage of as wide a combination of sources and techniques as possible. Lidar data alone cannot provide all the necessary information to understand the historic landscape, but when it is combined with more traditional techniques, as at Savernake, it can prove a very valuable tool.