Treasured Places In Focus
Aerial Survey at RCAHMS
Susan Casey, Treasured Places Research Officer
The exhilaration at discovering a long-buried site is an experience readily associated with the archaeological profession, yet in reality is one that few of us encounter in our working lives. For members of the aerial survey team at RCAHMS, however, it is a thrill with which they have become familiar. Since 1976, when a programme of regular flying began, well over 100,000 images have been taken and these have since revolutionised our understanding of Scotland's past.
Aerial survey can cover huge swathes of land and is often the only way in which sites reveal themselves. During hot, dry summers for example, cropmarks develop in arable crops over ploughed-down remains, while winter's low sunlight and snow showers can throw even the most innocuous bump on the ground into sharp relief, revealing long forgotten sites. The resulting photographs are an invaluable tool for archaeologists and planners, but the images can also be spectacular in their own right.
Capturing such images is not a matter of chance, as each time RCAHMS takes to the air the sortie has been carefully planned beforehand. Good teamwork is vital: a photographer sits with the pilot in the front of the plane, a small Cessna 172 single-engined aircraft, with a navigator and plotter in the back, behind the photographer. Working together, the aircraft is set on its route and positioned above sites for photography, and while photographs are taken out of an open window with the plane banked round hard to the left, targets are plotted on maps and navigation to the next site set in train. All this would be no easy task in normal circumstances, but is made even harder when the plane is banking, the window is open at 2,000 feet and cold air is rushing in. Good communication between the team members is essential - the volume of noise resulting from the open windows means clear instructions must be issued beforehand and the pilot and photographer rely on hand signals to navigate over and around the targets. A further staff member may also be squeezed onto the back seats, providing additional specialist knowledge while getting used to the working conditions so they can navigate in future.
The move from passenger to active participation in flights is one that RCAHMS Architecture Survey and Recording Officer Elaine Lee has experienced. The remit of aerial survey has gradually expanded to include photography of buildings, urban areas and civil engineering, for example, and this has many advantages - large developments and hospitals, for example, are readily appreciated from above. Elaine describes the aerial survey of buildings as a way of ‘seeing places that are familiar from a totally different perspective'. The photographs taken during the construction of the Scottish Parliament illustrate this point - showing the polygonal grouping of the new buildings developing opposite the regular square of Holyrood Palace.
Country houses and their estates also respond well to being photographed from above, illustrating the size and complexity of the policies surrounding Scotland's grandest homes. In the past, these estates would have dominated the surrounding landscape and the people who inhabited it - an aerial view is now often the only perspective that conveys some impression of this, in the face of encroaching urban developments and the gradual sale of policies.
This type of photography, showing buildings and their surroundings, is being used by Scotland's fire services in a very practical manner. The images are used to identify points of access and sources of water and contribute to the Fire Database, a project aimed at combating the significant loss of historic buildings to the effects of fire. The Project is a partnership between Historic Scotland, RCAHMS and the Scottish Fire Services.
Hot, dry summers provide a happy hunting ground for the aerial surveyor, searching out buried sites revealed by cropmarking, as arable crops grow at different rates above buried sites. The scorching weather of July 2006 resulted in exceptional cropmark formation and many previously unrecorded sites were discovered while a wealth of additional detail was visible at others. The Roman fort Trimontium (Newstead) is a particularly good example, where the visible detail includes the arrangement of the internal street plan and the gate towers. The importance of aerial photography is emphasised by the fact that in some parts of Scotland these cropmarked sites recorded on aerial photography has amounted up to 90% of the known archaeological sites in that area. David Cowley, Aerial Survey Projects Manager at RCAHMS, said: ‘Aerial survey remains the most effective way of recording sites and monuments rapidly across large areas, and for lowland areas where centuries of agriculture have buried many sites, it is the only way of seeing otherwise invisible remains. This overview underpins our understanding of where and how people in Scotland lived.'
New discoveries are not only made from the air. The process of cataloguing the images from each sortie frequently results in the discovery of new sites, and there is always the potential for further finds. In 2006, Peter McKeague, Database and GIS Projects Manager at RCAHMS, discovered a new site - a Roman temporary camp - on a photograph taken over ten years previously.
The collection of aerial photographs taken and archived by RCAHMS is unique and of great importance - illuminating Scotland's past, recording its present and providing for the future.