Introduction to Aerial Archaeology

What is Aerial Archaeology?

It is common opinion, that an aerial archaeologist is sitting in an aeroplane, trying to discover archaeological sites and to take a few nice photographs of them. This is (somehow) true. But aerial archaeology is more than just taking photographs, although this was and sometimes is still considered to be its main subject. In fact, it goes far beyond the mere acquisition of data, and you even donīt need photographs to perform aerial archaeology: you can use also satellite images, thermal images or airborne radar images. To perform aerial archaeology means above all, to make archaeological use of this kind of remotely sensed information. The terms "aerial" or "remotely sensed information" already indicate, how aerial archaeology works: it uses the distant view. Archaeological sites show up on the ground surface, depending on their state of preservation, by light-shadow-contrasts (shadow marks), tonal differences in the soil (soil marks) or differences in height and color of the cultivated cereal (crop marks). In that way, settlements, graveyards, fortifications etc. produce specific structures, that can be identified easier from a high viewpoint. In principle, you could see an archaeological feature also while standing on it, but like a cat on the carpet, you would not be able to realize any pattern, that could give you a bit more information about WHAT this site could be like. If You choose a more distant viewpoint (even if itīs only a ladder or a building), the structures become clearer to you and the pattern becomes understandable.

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MUSOV, Moravia This picture shows lines of still green crop, viewed from the surface.

(12Kb)	MUSOV, Moravia The same site photographed from the air. The green lines form a building complex made of wooden walls.

Aerial Archaeology and Prospection

Today, it is not only the upstanding remains of our cultural heritage, that is increasingly threatened with destruction. There is an even bigger amount of archaeological sites still hidden in the subsoil. Many of them are in a very bad condition due to intensive agriculture and the exploitation of our resources. Others are already vanished. If these were prior unknown - which comes true of a good deal - they are leaving irretreavable holes in the archaeological landscape. To prevent this, the archaeologist tries to detect, document and map archaeological sites, aiming to protect them or at least to extract from them as much information as possible, before they are destroyed. This is called "archaeological prospection". In the public opinion, archaeology is mostly connected with excavation. As a matter of fact, excavation is performed rather as a final step; it is somehow seen as the last resort to protect our cultural heritage by "destroying" a site scientifically, before it is deserted by bulldozers. Excavation of sites solely because of scientific interest is very rare nowadays. Today, the archaeologist is much more concerned with the non destructive protection of sites, which is - by the way - cheaper. Therefore, a broad range of prospecting techniques have been developed. Each of these prospection techniques has different aims, methods, advantages and drawbacks. None of them can be seen as the "non plus ultra". Aerial archaeology is one of the oldest prospection methods. It is very productive and (in relation to other methods) cheap, because you can cover quite a large area within a small number of flighing-hours and you can use any existing aerial photograph for your interpretation. A good example to illustrate this is the vertical aerial photograph of the area around Hornsburg in Lower Austria.

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HORNSBURG, Lower Austria Here, five archaeological sites can be detected within a single image, that was originally not even made for archaeological reasons. © Flugbildkompanie Langenlebarn

On the other hand, this picture shows also some of the limitations of aerial archaeology: there are plenty of factors (as soil type, climate, flying hour, vegetation etc...), which affect the visibility of sites. In many cases, as for example at the two middle neolithic ditch systems in our picture, only the mayor structures (in our case the ditches) show up on the surface. The settlements around them are in this photograph invisible, although they propably could be seen under different circumstances. Therefore, it is important, to combine different prospection techniques. Doing this, you can use the advantages of each, thus enabling optimized results. In Vienna, we have already experience in the combination of geophysical prospection with aerial archaeology.

Now, that you know, what aerial archaeology is about, you can go on and learn something about

	the history of aerial archaeology
	applications of aerial archaeology
	how and why do sites show up on the ground.