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| | Abstract | | The authors have started GPR survey for archaeology using GPR system combined with RTK-GNSS and HS350. The RTK-GNSS enables us to determine the horizontal position of the GPR antenna within 1cm and the vertical position within 1.5cm in real time. HS350 is the GPR antenna, made by GSSI in the US, adopted real-time sampling, and signal to noise ratio of the antenna is being improved by stacking the GPR waveform with several hundred times. Since both devices synchronize, we can achieve dense survey effectively. We conducted the GPR survey at Umamukazu burial mound where was located at the crowd of Iwabaru ancient burial mounds in Yamaga City, Kumamoto Pref. We measured 190 radial lines from the top to the bottom of the round burial mound with line-interval of 1.9 degrees. It was considered that a stone coffin which a dead body of regional powerful clan was placed was buried inside the round burial mound. And the survey lines of the GPR were arranged as surrounding the stone coffin from subsurface of the round burial mound. We calculated the emitted direction of radio waves if the surface of the round burial mound changed, and applied diffraction stacking method in three dimensional grids model using radially survey lines of 360 degrees. The results of the GPR imaging showed that remarkable reflections appeared in the depth range of 1.2m to 1.7m beneath the top of the round burial mound. Furthermore, we re-calculated focusing on the remarkable reflectors area with the 2cm grid size. Since the shapes of the remarkable reflectors considered as a stone coffin were complicated, we estimated that it might be traces after robbers excavated. |
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