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
In its original condition the EM— 31 type instrument cannot be used for the simultaneous measurement of both parameters (Re H, Im H). This together with the demand for automatic recording and the alphanumeric and graphic display of the data originating from a large number of measurements which can be carried out within a short time, justified the connection of a microcomputer to the instrument for data logging (Fig. 6). DATA STORAGE REPRESENTATION DATA PROCESSING I PLOTTING Y~ I _ T AUTOMATIC CONTROL AND SELECTION j PRINTING TAPE RECORDING DATA ACQUISITION VALIDITY CHECKING CORRECTION PRIMARY DATA PROCESSING fKA-160| |CE-158J HIGHER CAPACITY CALCULATOR HP-9845,HP.a6 MATRIX PRINTER (EPSON) FLOPPY DISKETTES I SHARP PC-<50Cl PTA-40 0 0 (calculator) t LUD Ell Fig. 6 Block diagram of the data storage and processing system of EM31 From the analogue output of the instrument the data are fed through an A/D converter to a PTA-4000 pocket computer extended to 28 Kbyte. The data collecting program is capable of storing 2000 measurements (2 parameters for each measurement) simultaneously. The field report is replaced by a data list printed by the computer. Data after the measurement are stored on a cassette tape recorder, but data transfer to an HP— 9845 computer and map drawing are also feasible. Automatic data storage has several advantages: besides speeding up the processing of data it eliminates the subjective errors of measurements and makes the simultaneous measurement of both channels possible as well. In the case of radio frequency measurements the apparent resistivity can be determined by the measurement of the distortion of the electromagnetic field of the distant radio transmitter. The depth of investigation with this method is generally greater than the depth of the objects under investigation in archaeology. Another disadvantage of the measurements - which can be performed otherwise quickly and simply - is low resolution and accuracy and that the opportunity to change the depth of investigation is small or it can be changed only within a hmited range because the direction of the transmitter and the frequency are fixed. Experiences described in the literature also show that the radio frequency method is not an ideal prospecting method in archaeology (Jolivet et al., 1977). By means of ground probing radar the detection of layer boundaries having a resistivity or dielectric constant contrast is possible. The equipment generates electromagnetic pulses on the surface and records the signals reflected from the layer boundaries with different geoelectric characteristics by means of a wide-band receiver antenna. The recording of the reflection profile is similar to that of the single-channel seismic profile: the resulting profile comprises the transmitter pulses and the waves reflected from the layers below the surface (GSE, 1976). This method has high resolution and enables continuous profiling. ~ .
