**Author details**

**4. Results and conclusions**

and the depth range.

**Acknowledgements**

Interactive transparent 3D visualizations of GPR data volumes were produced for each part of 6 human statues and a group of 24 lion sculptures at Anitkabir, Turkey. We produced images of natural internal cavities and fractures within the statues via a proposed method of interac‐ tive transparent 3D half bird's-eye visualization of the GPR data volume of the profile range

134 Imaging and Radioanalytical Techniques in Interdisciplinary Research - Fundamentals and Cutting Edge Applications

Our first approximation related to amplitude–colour simplification. This allowed us to differentiate and locate native micro-cavities and micro-fractures inside the statues, based on radargrams of the profiles gathered on the surface of the statues. The second approximation related to our proposed opacity function, which dominated maximum positive and negative amplitudes and eliminated other irrelevant amplitudes. Third, an interactive transparent 3D half bird's-eye view of the 2D GPR data set was achieved by carefully assigning the amplitude– colour scale and its opacity range, together with a carefully selected viewing angle, profile and/ or depth range. The transparent 3D imaging proved successful in identifying changes in the statues, accurate *x–y* locations and accurate depths. This monitoring replied to the aim of the study. Mapping fractures and cavities within statue groups could enable evaluation of their

In the fourth approximation, the present study developed an improved amplitude-balancing approximation in order to reveal and differentiate subsurface historical remains from the surrounding soil medium. By combining the second and third approximations, the balancing of the amplitude–colour scale achieved sufficiently high resolution to represent the remains with the same colour ranges on both the slices and their transparent 3D imaging with increas‐ ing depth axis. A viewing angle was allocated to the x, y and z axes of the 3D data-volume by checking wall orientations and the data measurement directions on the map to obtain a good half bird's-eye view. The transparent 3D half bird's-eye view of the 2D GPR data set provided better imaging to accurately visualize the subsurface by sensing x–y locations and depths. The results demonstrated that the GPR method and our developed 3D visualization gave perfect results in a closed, circular area including remnants of very complex buried foundational wall, including a cemetery, within the Zeynel Bey tomb without any risk of damage to the tomb and infrastructures. In addition, the results also indicated that the visualization method perfectly monitored the archaeological buried walls with accurate x–y locations and accurate depths.

We also indicated that GPR method provides highly accurate results for the position and depth

The authors would like to thank the military authorities at ANITKABIR; KA.BA Conservation of Historic Buildings and Architecture Ltd. with the coordination of rescue excavation director Prof. Dr. Abdüsselam Uluçam, Rector of Batman University, Turkey; and Ankara University

stability and indicate the best way to minimize restoration costs.

of targets within very complex and restricted areas, even on statues.

Selma Kadioglu1,2\*

Address all correspondence to: kadioglu@ankara.edu.tr

1 Ankara University, Faculty of Engineering, Department of Geophysical Engineering, Ankara, Turkey

2 Ankara University, Earth Sciences Application and Research Center, Ankara, Turkey
