M. Járó - L. Költő szerk.: Archaeometrical research in Hungary (Budapest, 1988)

Prospecting - CSATHÓ Beáta, PATTANTYUS-Á. Miklós: Possibilities and experiences of geophysical prospecting at archaeological sites in Hungary

results are determined not only by the investigated object but geological and other (e. g. cultural) noises may also influence them. Therefore the homogeneity of the environment is a very important prerequisite for successful measurements. In an inhomogeneous area the investigated object should have significantly different parameters so as to be able to recognize its effect correctly. In addition, the ratio of the size to the depth of the investigated body must be considered as well : detectability decreases as a function of depth. In view of all these conditions, it generally has to be examined at each prospecting site whether a certain geophysical method is suitable for the detection of the supposed target or not. If the object has physical parameters on the basis of which it can be distinguished from its environment, then the type of instruments and methods by which it can be prospected, even in the case of high background noise, must be determined. The aim of geophysical prospecting in archaeology It evolves from the fact mentioned above that geophysical prospecting is rarely suitable for finding entirely unknown archaeological objects or sites. It is much more suitable for determining and delineating the extent and exact location of already found or supposed objects and for marking out areas that maybe worth excavating thus reducing the number of superfluous trial trenches. Geophysical methods, however, should not be overestimated. They do not exempt archaeologists from excavation but inform them where it is worth digging. In some exceptional cases the geophysical survey of an area provides such a complete image that a well-founded archaeological interpretation is possible even after a small scale excavation. This occurs rarely, however, and interpretation not supported by excavation must be treated carefully. It may also happen that archaeological excavation is hindered by a high water table or some structures through which excavation is impossible, but surface measurements can be made. In such cases, an acceptable result — which can be rendered probable - is still better than the absolute lack of information. The requirements related to the applicable geophysical methods The requirements related to the geophysical methods applicable in archaeology can be summarized as follows: high resolution necessary for separating the effect of the structures; small and changeable investigation depth necessary for examining different depth intervals; quickness and rentability. This means that simple, portable geophysical instruments are needed which are easy to handle and provide rapid and easily interprétable results. Computer data collection and preliminary on site data processing are the main prerequisites of immediate interpretation. Let us summarize the types of features in archaeological prospecting, in respect of geophysics — apart from their age which is irrelevant as far as surface measurements are concerned - and the methods suitable for detecting them. Magnetic and geoelectric methods are the most frequently and widely used because most objects have characteristic magnetic susceptibility and electric resistivity differing significantly from those of the environment, and the interpretation of the parameter maps is relatively simple.