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

Prospecting - ERDÉLYI Balázs, PATTANGYUS-Á. Miklós: Computer image processing and soil resistivity survey of an archaeological site discovered by aerial photography

This filter was rotated until the feature took shape (i.e. in the case of filtering in the wrong direction, the anomalies fall apart) and, in fact, it was the residual filter of NW-SE direction which provided an acceptable result. Interestingly, it is not from the zones of higher or lower resistivity that the linearity can be seen well, but the effect looked for appears in a characteristic manner in the values of the horizontal gradient. This is why a (residual) filter of 0 sum had to be applied which, in the case of edge filter, provides a picture about the increasing density of the changes in a given direction (Fig. 4). N Fig. 5 Apparent resistivity maps measured with an E-W layout direction (see Fig. 2). A: map constructed from the measured values, on which zones of resistivities deviating from the average can be traced, similar to Fig. 3; B: filtered version of map A according to the caption of Fig. 4 (gradient map). On this map, however, theN-S direction of the earthwork perpendicular to the layout direction cannot be traced unambiguously. On the raw anomaly map of the electrode array with a direction perpendicular to that of the previous one (Fig. 5, A) — i.e. on the map on which the linearity of N-S direction was expected to appear - at most the effects described so far can be observed. Moreover, on the similarly (corresponding to this direction) filtered anomaly map, only the conclusions already drawn can be stated (Fig. 5, B). From this map no reliable information of the N—S direction of the earthwork could be obtained. Figure 6 shows the axonometric picture of the resistivity map measured with a N—S layout direction and filtered by a weighted average filter (of 1 sum), but by a suitably rotated symmetric edge filter. The direction of the characteristic feature interpretered above is indicated by arrows.