## 6 Case Projects
### Synagogue in Amezrou  
The synagogue in the city of Amezrou (near the Zagora, Figures 9 and 10) is a unique monument, now under reconstruction. It is a unique triangular synagogue (approx. 7 \(\times\) 7 \(\times\) 10 m\({}^{3}\)) located in the _mellah_, which was a part of the old town. The synagogue was documented and mapped with the help of both laser scanners (BLK360 and ZEB-REVO) (Figures 11 and 12). The main aim for historians and architects was to get a precise shape and orientation of this sacral place. The demonstration of new technologies was also intended for local monument care specialists, who gave us a short and rare opportunity to see the place.  
Figure 9: Graphical view on the captured point cloud coloured by hight.  
Figure 11: Point cloud from ZEB-REVO (a camera for texturing is not included in this model).  
Figure 12: Textured point cloud from BLK360.  
Figure 10: Synagogue in Amezrou (inside BLK360 laser scanner).  
By using of ZEB-REVO, the synagogue was measured in three minutes only by walking through synagogue. There are no other characteristics that would indicate the quality of the measurement. Processing is completely automatic. The only option is to use control points or compare with a model obtained from a more accurate device.  
Photogrammetry was made on this place as a technological experiment only. Due to insufficient lighting for high-quality close-range photogrammeters, images were taken only by a mobile phone (iPhone 7:12 MPix camera with 4 mm focal length, Sony Exmor RS 1.22 um pixel size). One hundred and forty-one overlapped images were taken in 15 min. A model created from the photographs was not sufficient and missing parts occurred because 10% of all photos was not possible to orient due the shadows and low overlap (Figure 13). The factors that determine the quality of the produced 3D model are mainly lens distortion, low-resolution in texture mapping, low lighting leading to the image blurring, and colour blurring on the image border. Of course, a smartphone is not ideal equipment and it was not the goal to use precise photogrammetry with this camera (Table 3). However, the camera quality in smartphones is constantly improving and with the right photographing process, the results may be satisfactory for smaller subjects. In this case, it was just a test, which shows that low-cost close-range photogrammetry without precise preparation can get insufficient results (Figure 13), but in other cases for documentation of small artefacts for example, it gives results of sufficient quality with sub-millimeter GSD (ground sample distance). The results from all technologies are shown in Figures 14 and 15.  
The orientation of the synagogue was measured using the iPhone build-in compass. This is for information only, showing how the synagogue is oriented. No correction was applied because the magnetic declination is here only 0.66 degrees. In the Jewish sense, the altar is a cabinet built into the front wall of the synagogue and it contains Torah scrolls. The altar is directly to the east, and in the model, it is a built-in cabinet located behind the tip of the triangle. A precise orientation (east-west) was measured also in other documented synagogues (Figure 16).  
Figure 14: Ground schemes from ZEB-REVO (**a**), BLK360 (**b**), and iPhone (**c**); you can see that with the handheld scanner, the spaces behind the wall (behind the tip of the triangle) can also be documented. The model from photos, taken by an iPhone 7, was not very good due to bad lighting, inappropriate texture, combined with a short time for taking photos; however it is not a typical result from close-range photogrammetry, that can create high-quality 3D models.  
Figure 15: The ground-plan of the synagogue from the point cloud (ZEB-REVO).