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

1m — AB — —MN—0-2 2 T ^ T 7 2 T, Y 2 2 o c V b Q m Fig. 2 Sheme of the dipole-dipole array: a- surface, b. location of the prearranged electrodt along a profile, c reference points of the measured data corresponding to the given dipoi At the beginning of the prospecting of an area a few profiles are measured witl several dipole distances; then, after selecting the most characteristic ones, the area i: surveyed by only two AB—MN distances. Information from different depths is necessary not only to eliminate noise and disturbances but also to enable one to determine tht depths of the objects below the surface. Since the measurements are generally performed above inhomogeneous layers their results are influenced by the layout directions. It would be ideal to measure an area with two layout directions perpendicular to each other. It is not, however, always possible due to economic considerations. Therefore, in the case of presumably linear structures, we try to select the layout direction so that it is perpendicular to the direction of linearity since in this case the current distribution is most favourable for enhancing the effects. Experiments are also made for simultaneous, multi-direction resistivity measurements (e. g. square-array: Bolton, 1984; and Hesse et al, 1986). In the case of non-linear objects generally even measurements in one direction provide satisfactory results (see: Jászdózsa, in this volume, pp. 53—57 ). Most of our successful surveys in the past years were performed by resistivity profiling. We applied them successfully to the prospecting of walls and building remains, to the prospecting of settlements, and to the localization of a prehistoric flint mine (Pattantyús-Á., 1986). In this last case the changeability of the depth of investigation is of extreme importance since unlike at the majority of archaeological problems, where it is advisable to have a more or less close estimation of the depth of investigation, in the case of this flint mine it was unknown. The measuring results are usually evaluated by mathematical or analogue modelling. Figure 3 shows a resistivity profile which was calculated by mathematical modelling and it shows the apparent resistivity profile measured above a buried stone wall. It was evaluated by the theoretical curve. The convolution filtering of resistivity profiles (see: Balácapuszta, pages 46, 47 ), and the handling of resistivity maps by filters of various transfer characteristics and purposes may be a great help for interpretation (see: Turkeve, pages 35—41). The first step has-been taken to increase the productivity of resistivity measurements; a data logger was fitted to the measuring equipment. The connection of a data logger to a computer makes primary fie Id-processing and display possible, similarly to the examples that can be found abroad (Kelly et al, 1984). distance