Monitoring buried remains with a transparent 3D half bird's eye view of ground penetrating radar data in the Zeynel Bey tomb in the ancient city of Hasankeyf, Turkey
The aim of this paper is to show a new monitoring approximation for ground penetrating radar (GPR) data. The method was used to define buried archaeological remains inside and outside the Zeynel Bey tomb in Hasankeyf, an ancient city in south-eastern Turkey. The study examined whether the proposed GPR method could yield useful results at this highly restricted site, which has a maximum diameter inside the tomb of 4 m. A transparent three-dimensional (3D) half bird's eye view was constructed from a processed parallel-aligned two-dimensional GPR profile data set by using an opaque approximation instead of linear opacity. Interactive visualizations of transparent 3D sub-data volumes were conducted. The amplitude-colour scale was balanced by the amplitude range of the buried remains in a depth range, and appointed a different opaque value for this range, in order to distinguish the buried remains from one another. Therefore, the maximum amplitude values of the amplitude-colour scale were rearranged with the same colour range. This process clearly revealed buried remains in depth slices and transparent 3D data volumes. However, the transparent 3D half bird's eye views of the GPR data better revealed the remains than the depth slices of the same data. In addition, the results showed that the half bird's eye perspective was important in order to image the buried remains. Two rectangular walls were defined, one within and the other perpendicularly, in the basement structure of the Zeynel Bey tomb, and a cemetery was identified aligned in the east-west direction at the north side of the tomb. The transparent 3D half bird's eye view of the GPR data set also determined the buried walls outside the tomb. The findings of the excavation works at the Zeynel Bey tomb successfully overlapped with the new visualization results.