International Conference on GPR in Archaeology (Nara, February 2001)

GPR survey with the study of dielectric property on the moat structure at the archaeological remains

Takayuki NAKANO and Hideo SAKAI

Ground Penetrating Radar (GPR) probing has been conducted at the following two archaeological remains to detect the moat and/or ditch structure.

(1) Shozui site: a manor house of powerful family at medieval ages, in Aizumi town, Tokushima Prefecture.

(2) Yanaida-nunooyama site: a mounded tomb in Himi City, Toyama Prefecture. It's the biggest keyhole tomb with quadrangular rear mound in the Japan-Sea side area.

At the Shozui site, GPR survey was done at 20 survey lines. The found structure of ditch is concordant with the excavation study. The ditch has the width of 10m and 4m depth.

At the Yanaida site, survey was conducted at over 300 lines (each line is 10-20m length). The analyzed results clearly show the three dimensional structure of moat surrounding the mound. The estimated width and depth of moat differs between the area of front, side and rear site of mound. That is, the clear structure of moat is analyzed in the front site whose width is c.a. 10m and the depth is 2-2.5m. The moat in the side site seems to show the wider (-15m) and shallower structure. In the rear site, no clear moat is found. Also, the bridge structure is suggested at the corner of front site.

Excavation study carried out at several regions shows the concordant feature of moat with the result by GPR prospecting.

(3)Measurement of dielectric property of soil

GPR survey analyzes mainly the dielectric property underground. We collected the soil at the several depths from the excavated area of moat and then conducted the measurement of relative dielectric constant (RDC). The Q-meter was used in the study. The RDC structure of the soil of moat is concordant with the estimated dielectric feature underground by GPR survey.

Both archaeological sites in this study are cited as the "the national designated archaeological site of Japan", in November 2000.

Return to conference page