**2.4. Transparent 3D half bird's-eye view of GPR data set**

Generally, interactive visualization is carried out by constructing 3D data volumes of parallelaligned 2D GPR data sets to show the target objects. The 3D data volume can be displayed as slices, including profiles, times (or depths) and common traces of the profiles; or separated sub-blocks are rendered as solid iso-volumes with linear opacity, determined by the amplitude of the anomalies. The buried fractures or cavities can be defined on the interactive slices, particularly on depth slices with location, and shapes according to depth. Therefore, it was necessary to check the most meaningful depth slices and profiles to define the structures of the subsurface if the area is small and complex. However, the obtained results could be further improved.

Our aim was to obtain a good 3D data volume display, which was a critical part of interpreting the GPR data set. The 3D image is able to present a view of subsurface features such as a fracture or cavity, in addition to objects such as industrial and/or archaeological remains, etc. This imaging could be achieved by a transparent 3D half bird's-eye view revealing only buried objects. Therefore, firstly, transparency could be achieved by constructing an opacity function instead of linear opacity determined by the amplitude scale (Figure 8). The horizontal axis of the opacity function was the amplitude scale starting with maximum negative amplitude and ending with maximum positive amplitude; the vertical axis represented opacity coefficients of the amplitude range [11, 23]. Thus, any amplitude range could be highlighted or minimized by the appointed opacity coefficient. The REFLEXW program allows the opacity coefficient to be chosen between one (maximum opacity) and zero (transparent) (Figure 8b) [26]. A trans‐ parent view could be obtained only by eliminating the unwanted amplitude range.

Therefore, the amplitude range was important. Because it was known that the maximum amplitudes represented discontinuities, the weak amplitude range was eliminated by giving these a zero opacity value, and transparent 3D imaging was obtained. The transparency was achieved by allocating an opaque interval to the amplitude scale, similar to the re-arranged amplitude–colour approximation for interested profile range or time range for the solid 3D GPR data volume. This visualization type was applied to both the statues and archaeological remains in this chapter. Figure 9a indicates traditional, solid depth-slices, while Figure 9b indicates transparent depth slices at 15 cm, 38 cm and 51 cm of the data set for the skirt of the first female statue. These slices were used to control micro-fractures and cavities according to the skirt thickness. The horizontal x-axis and y-axis of slices indicate the profile sequence and the distance along the measuring profile respectively. Locations of the micro-cavities could be seen on the slices. It is necessary to carefully check interactive slices in order to determine location and shapes according to depth (thickness).

**Figure 9. (a)** Traditional solid depth slices at 15 cm, 38 cm and 51 cm, **(b)** Transparent depth slices for the skirt of the

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The horizontal axis of the amplitude–colour function (Figure 7) is the amplitude scale of the GPR data, whereas the vertical axis represents colour categories from 0 to 255. The colour

first female statue (same three depths).

**Figure 10. (a)** Solid 3D GPR data volume visualization of the skirt of the first female statue (Figure 5) with all profiles and depth range through special view angle of profile slices, **(b)** transparent half bird's-eye views of the same 3D data volume of (a).

Secondly, it was necessary to arrange viewing angles of the x, y and z axes, to obtain the maximum meaningful 3D data volume for the relevant depth range or profile range. The slices could be interpreted differently with differing viewing angles, although the visualization of the slices was required to be the same with the data measurement axes on the map or on a picture. However, there was a general lack of knowledge about the subsurface, including the remains, and about when to take data measurements with regard to information such as the direction of a fracture or an archaeological wall. Therefore, the data measurement strategy was decided according to the field size.

10b and 11b represent our approximation with the transparent 3D half bird's-eye view visualization of the same data set. The horizontal x-axis of Figure 10 and Figure 11 indicates the distance along the profile. The horizontal y-axis represents the profile sequence. The vertical axis indicates thicknesses of statues from the front surface to the back surface of the skirt of the statue. Figure 12 shows different depth ranges of transparent 3D half bird's-eye views of the GPR data aligned on the first female statue (Figures 5 and 11b) between 0–10 cm, 10–20 cm, 20–30 cm 30–40 cm, 40–50 cm and 50–60 cm depth ranges, and shows the locations of the micro-fractures and cavities with purple and blue colours, represent the maximum amplitude ranges. Figure 13 indicates different profile ranges of transparent 3D half bird's-eye views of the GPR data aligned on the skirt of the first statue (Figures 5 and 10b) between profiles 1–3, profiles 4–6, profiles 7–9 and profiles 10–11; and the upper part of the female statue between profiles 1–3 and profiles 4–8 through special viewing angle of the profile slices; the

**Figure 11. (a)** Solid 3D data volume visualization of the skirt of the first female statue (Figure 5) with all profiles and depth range through special viewing angle of depth slices, **(b)** transparent half bird's-eye visualization of the same 3D

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data volume in (a).

locations of micro-fractures and cavities are represented by purple and blue colours.

The slices obtained with the same axes on the map of the study site could not effectively represent the subsurface. In addition, when the slices were rotated around the axes, a lining fracture or a wall along the same direction as the angle of view of the slice could be imaged more effectively than in the standard view. To image the fractures and native cavities in the statues, it was decided to use a transparent 3D sub-volume of the profile and depth slices with a half bird's-eye view by arranging the view angles of the axes. Figures 10a and 11a indicate the solid 3D data volume visualization of the skirt of the first female statue with all profiles and depth range using a special viewing angle of profiles and depth slices. In addition, Figures

**Figure 11. (a)** Solid 3D data volume visualization of the skirt of the first female statue (Figure 5) with all profiles and depth range through special viewing angle of depth slices, **(b)** transparent half bird's-eye visualization of the same 3D data volume in (a).

Secondly, it was necessary to arrange viewing angles of the x, y and z axes, to obtain the maximum meaningful 3D data volume for the relevant depth range or profile range. The slices could be interpreted differently with differing viewing angles, although the visualization of the slices was required to be the same with the data measurement axes on the map or on a picture. However, there was a general lack of knowledge about the subsurface, including the remains, and about when to take data measurements with regard to information such as the direction of a fracture or an archaeological wall. Therefore, the data measurement strategy was

**Figure 10. (a)** Solid 3D GPR data volume visualization of the skirt of the first female statue (Figure 5) with all profiles and depth range through special view angle of profile slices, **(b)** transparent half bird's-eye views of the same 3D data

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The slices obtained with the same axes on the map of the study site could not effectively represent the subsurface. In addition, when the slices were rotated around the axes, a lining fracture or a wall along the same direction as the angle of view of the slice could be imaged more effectively than in the standard view. To image the fractures and native cavities in the statues, it was decided to use a transparent 3D sub-volume of the profile and depth slices with a half bird's-eye view by arranging the view angles of the axes. Figures 10a and 11a indicate the solid 3D data volume visualization of the skirt of the first female statue with all profiles and depth range using a special viewing angle of profiles and depth slices. In addition, Figures

decided according to the field size.

volume of (a).

10b and 11b represent our approximation with the transparent 3D half bird's-eye view visualization of the same data set. The horizontal x-axis of Figure 10 and Figure 11 indicates the distance along the profile. The horizontal y-axis represents the profile sequence. The vertical axis indicates thicknesses of statues from the front surface to the back surface of the skirt of the statue. Figure 12 shows different depth ranges of transparent 3D half bird's-eye views of the GPR data aligned on the first female statue (Figures 5 and 11b) between 0–10 cm, 10–20 cm, 20–30 cm 30–40 cm, 40–50 cm and 50–60 cm depth ranges, and shows the locations of the micro-fractures and cavities with purple and blue colours, represent the maximum amplitude ranges. Figure 13 indicates different profile ranges of transparent 3D half bird's-eye views of the GPR data aligned on the skirt of the first statue (Figures 5 and 10b) between profiles 1–3, profiles 4–6, profiles 7–9 and profiles 10–11; and the upper part of the female statue between profiles 1–3 and profiles 4–8 through special viewing angle of the profile slices; the locations of micro-fractures and cavities are represented by purple and blue colours.

continuities of micro-fractures and cavities within very restricted study areas, such as those in

**Figure 13.** Transparent half bird's-eye results of the 3D sub-volumes shown in Fig. 10b between profiles 1–3, profiles 4–6, profiles 7–9 and profiles 10–11; and the upper part between profiles 1–3 and profiles 4–8 through special view‐

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ing angle of profile slices, including internal micro-fractures and cavities.

The native micro-cavities are not effective to harm the lions. The micro-fractures show a lateral, inclined or vertical linearity. According to Figures 12 and 13, the skirt of the statue had an important fracture between profiles 1 and 3, ranging from 0–80 cm from the front surface as far as the back surface. In addition, the figure had more small fractures and native cavities between 0- and 30-cm depth. To summarize to our method, we present results from the transparent 3D half bird's-eye view of three GPR data sets gathered form the backs of three lion sculptures, using three parallel-aligned profiles along the leg and head to visualize interior

According to the visualization results in the first lion, there were three large fractures aligned parallel to the surface along the back legs, which continue from the upper surface of the back legs to the border lion along the depth; and there were native cavities in the back through the belly. The second lion mostly had disorderly native cavities and micro-fractures along the back surface until the belly. The last lion was seen very powerful, and only included some native

the present study.

fractures (Figure 14).

cavities in the back side.

**Figure 12.** Transparent half bird's-eye view results of the 3D sub-volumes of Figure 11b between 0–10 cm, 10–20 cm, 20–30 cm, 30–40 cm, 40–50 cm and 50–60 cm depth ranges, respectively, including internal micro-fractures and na‐ tive cavities.

The profile ranges of Figure 13 give the locations of the fractures and cavities throughout the depth of the profile ranges, while the depth ranges of Figure 12 give the locations of the fractures and cavities along the full surface of the skirt through the depth ranges. Therefore, it is possible to check both transparent profile ranges and depth ranges according to the most appropriate viewing angle of the 3D GPR data volume in order to determine the locations and

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**Figure 13.** Transparent half bird's-eye results of the 3D sub-volumes shown in Fig. 10b between profiles 1–3, profiles 4–6, profiles 7–9 and profiles 10–11; and the upper part between profiles 1–3 and profiles 4–8 through special view‐ ing angle of profile slices, including internal micro-fractures and cavities.

continuities of micro-fractures and cavities within very restricted study areas, such as those in the present study.

The native micro-cavities are not effective to harm the lions. The micro-fractures show a lateral, inclined or vertical linearity. According to Figures 12 and 13, the skirt of the statue had an important fracture between profiles 1 and 3, ranging from 0–80 cm from the front surface as far as the back surface. In addition, the figure had more small fractures and native cavities between 0- and 30-cm depth. To summarize to our method, we present results from the transparent 3D half bird's-eye view of three GPR data sets gathered form the backs of three lion sculptures, using three parallel-aligned profiles along the leg and head to visualize interior fractures (Figure 14).

**Figure 12.** Transparent half bird's-eye view results of the 3D sub-volumes of Figure 11b between 0–10 cm, 10–20 cm, 20–30 cm, 30–40 cm, 40–50 cm and 50–60 cm depth ranges, respectively, including internal micro-fractures and na‐

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

The profile ranges of Figure 13 give the locations of the fractures and cavities throughout the depth of the profile ranges, while the depth ranges of Figure 12 give the locations of the fractures and cavities along the full surface of the skirt through the depth ranges. Therefore, it is possible to check both transparent profile ranges and depth ranges according to the most appropriate viewing angle of the 3D GPR data volume in order to determine the locations and

tive cavities.

According to the visualization results in the first lion, there were three large fractures aligned parallel to the surface along the back legs, which continue from the upper surface of the back legs to the border lion along the depth; and there were native cavities in the back through the belly. The second lion mostly had disorderly native cavities and micro-fractures along the back surface until the belly. The last lion was seen very powerful, and only included some native cavities in the back side.

**3. Picturing buried archaeological remains and foundational**

Our new 3D visualization was applied to archaeological remains both inside and outside the Zeynel Bey tomb in the ancient Turkish city of Hasankeyf. This site is among the last remaining locations of the Silk Road in Anatolia, spreading towards the East, and is located in Batman province, southeastern Turkey (Figure 15). A similar type of visualization for archaeological

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The precise foundation date of Hasankeyf is not known. The geopolitical situation in Hasan‐ keyf strengthens the possibility of its being a very ancient settlement area. Hasankeyf is identified with the tomb built by Uzun Hasan for his son Zeynel Bey, who died in the war of Otlukbeli (1473) by the Tigris [34]. The Zeynel Bey tomb, the first example of the Anatolian mausoleum tradition (Figure 16), is on the north bank of the Tigris, across from the city.

The tomb is a cylinder of diagonal patterns made using brick and tile, with a pointed arch portal doorway on the north and a window in the south wall (Figure 16). Above the main shaft is a slightly smaller diameter shaft, which has small windows in each of the cardinal directions and carries a hemispherical dome (Figures 16 and 17) [34-37]. Inside, the plan is octagonal, with muqarnas niches supporting the transition to the round base of the dome. Each of the eight walls has a rectangular arched niche, and the burial chamber is recessed into the floor

**Figure 15.** Geographical map of the Zeynel Bey tomb in Hasankeyf ancient city, Turkey.

**3.1. Zeynel Bey tomb in Hasankeyf ancient city**

remains was introduced by previous studies [26, 33].

**infrastructures**

(Figure 17) [36].

**Figure 14. (a)** One of the 24 lions on the Lion Road, **(b)** data acquired from three parallel profiles from the back to the head of the lion, **(c)** the results of the transparent half bird's-eye view of the three different lions.
