The Hirui-Otsuka mounded tomb located in Ogaki City, Gifu Prefecture, Japan, dates back to the late fourth century AD. A resistivity survey was carried out in order to acquire detailed information about the central burial on the top of the mound. A 23.5 m by 16.5 m rectangular area was surveyed, and 34 measurement lines each with a length of 23.5 m were measured at intervals of 0.5 m. The Wenner configuration was adopted; electrode spacing was changed from 1.0 m to 4.0 m by 0.5 m, and the measurement point was shifted at intervals of 0.5 m. The number of samples reached 7854, but it took only 7 h to measure such huge a data set by the use of a computerized multi-electrode system developed by the authors. The central burial was observed as a low-resistivity anomaly. However, it differed from the result of a previous ground-penetrating radar survey. If the central burial was a stone chamber, it would be observed as a high-resistivity anomaly. By a computer simulation, the authors were led to an interpretation that the central burial was a stone chamber covered by a layer of clay.
An experimental measurement of temperatures of the ground was carried out in order to confirm whether they could provide information on the existence of subsurface archaeological remains. Four thermoresistances were arranged on top of the mound at a depth of 0.5 m, one of them was placed over the central burial. The measurement was carried out continuously for 38 h. It was observed that the ground temperature over the central burial had a different pattern of change from those of other positions. Copyright *