The Ground Probing Radar (GPR) geophysical surveying system is based in the ordinate emission to the subsoil of electromagnetic pulses of a known frequency and duration, and the recording of the reflections generated when they reach different layers and elements in the subsoil.
Until recently, this information was imaged only through the radargram, which provides information on the horizontal axis and time (or depth, if the travel velocity of the electromagnetic pulses through the subsol is known), on the vertical axis.
SOT uses since 2003 the time-slicing visualising technique, which provides a more comprehensive imaging of the results of GPR surveys. Thanks to this technique, the interpretation of results can be discussed between the geophycist and the archeologist, given that the extension and volumes of the detected features can be visualised in plans, sections and volumes recreations, instead of radargrams.
SOT uses a SIR-3000 GPR system (GSSI) with 400MHz and 270MHz antennae (exploration depth up to 3m and 5m, respectively).