The Commission has two categories of Aerial Photography records
- Existing evidence of human activity (urban and rural, current and historic)
- Archaeological Surveying of open land and smaller areas not built on.
For Activity 1
A large collection of aerial photographs obtained from Aerofilms Ltd (formed in 1919) and from smaller collections and from the RAF survey records is held by each of the Commissions for Scotland and Wales and by English Heritage. These form the main content of the online “Britain from Above” project.
For Activity 2
The Commissions are the main providers of Aerial Surveys and processes.
Dr Toby Driver is the Aerial Investigator for the Commission in Wales and whilst being mainly involved in Activity 2 also has a role in Activity 1 in recording the ongoing land development in Towns and the countryside. There are two natural effects which assist in aerial surveying for archaeological purposes. The most useful is the effect of vegetation growth on land surfaces with underlying impervious layers revealing shapes and patterns below ground which may indicate historic activity now covered over. The second effect uses the shadow cast by sunlight on the shapes and forms on the land surface which are more easily discernable from altitude than at ground level.
Covered Building foundations and floor areas and road and trackways have been discovered by analysing vegetation growth differences. Shadow effects have been used to identify man made mounds or ditches and weathered way routes. Appropriate conditions are required to undertake surveys e.g. Clear air, time of day for altitude of the sun. Semi drought conditions enhance vegetation differences and ground frosts give better visual contrasts of ground level forms. Technical advances in recent years have enabled greater accuracy and provided more detail in aerial survey surface investigations. The use of new laser ranging technology called LIDAR has enabled more accurate plotting of ground features even in areas hidden by trees.
Aerial surveys in Wales range from Iron Age forts c700BC and later enclosures including traces of dwellings, to Roman roadways connecting their fort sites and through to Medieval times and early Industrial Revolution sites. A recent aerial survey provided the first evidence in West Wales of a Roman villa at Abermagwr close to a fort at Trawscoed. Many aerial surveys provided first time evidence of discoveries whilst later surveys provided additional information and clarifications. The identification of possible aerial survey sites arise from the study of early manuscripts or from land form indications such as possible valley settlements.
Aerial surveys are undertaken in two-seater high wing light aircraft operating from Withybush, Haverfordwest. Survey routes near to MOD sites or the drone testing site at Aberporth must be agreed with the Air Ministry. Future surveys may use unmanned drones but the larger types, whilst having an extremely useful technical ability are expensive to operate and are currently used exclusively by the military. Smaller ‘Hobby’ equipment are now available and affordable but will need to go through a teething period of random and irresponsible use before becoming acceptable for survey work. They may then provide an useful increase in amateur and professional aerial surveys and a modest expansion in our knowledge of our history and current development.
We may assume that Dr Driver will continue in gainful, employment adding to our knowledge and enjoyment of Wales from the Air.