## 4 Methodology  
The aim of the documentation was plans and cross-sections of buildings, especially roofed _mellahs_, as well as 3D documentation of buildings or special spaces like synagogues. The basis was therefore always spatial measurement. From the point of view of methodology, all technologies (MLS, TLS, and IBMR close-range photogrammetry) were used (Figure 7).  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Instrument** & **Accuracy** **[mm]/on 10 m** & **Range** **[m]** & **Speed of Scanning** **[points]/s** & **Approx. Data** **[point]/s** & **Time** **[min]** & **Instrument** **Approx. Price** **[K \(\xi\)]** \\ \hline BLK360 & 4 & 30 & 360,000 & 0.6/1 scan & 6 per scan/middle resolution & 30 * \\ ZEB-REVO & 10–20 & 30 & 48,000 & 0.1/per five min & slow walking speed & 30 * \\ Photogrammetry & 5–20/depend on & & & Up to 30 & \\ IBMR (a DSLR, & camera type and on & & photos/min & 0.04/per photo & Up to 30 & 1 ** \\ here Canon 450) & distance & & & & photos/min & \\ iPhone 7 camera & 5–50 depend on & & & & \\ distance & & & & & \\ \hline \end{tabular}
\end{table}
Table 2: Comparison of accuracy and economy of the process (* including software, ** without software price—we use the university license, which is only 0.6 K \(\xi\)).  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Instrument** & **A [m]** & **B [m]** & **C [m]** & **D [m]** & **E [m]** \\ \hline Leica Disto A5 & 5.761 & 0.835 & 3.771 & 1.048 & 1.166 \\ Leica TCR 307 & 5.758 & 0.835 & 3.758 & 1.056 & 1.174 \\ Surphaser 25 HSX & 5.761 & 0.836 & 3.781 & 1.049 & 1.169 \\ Leica BLK 360 & 5.767 & 0.833 & 3.775 & 1.043 & 1.164 \\ ZEB-REVO & 5.785 & 0.850 & 3.779 & 1.028 & 1.174 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Results of selected measured distances (A, B, C, D, E) using different instruments.  
The hand-held PLS ZEB-REVO was used as the basic device and photogrammetry and TLS were used as complementary technologies. It must be said that each has its advantages and disadvantages and their use is different for different objects.  
The PLS is speedy, mobile, and ideal for mapping larger built-up areas; in the case of the ZEB-REVO there is no texture, because the ZEB-REVO scanner used here does not have a camera and only creates a non-textured point cloud. It has an accuracy within 1 cm, which was sufficient for the purposes of expedition and given objects, and it means often considerably decayed _mellals_. TLS is more laborious, while with the BLK360 there is texture and higher accuracy (Figure 8); the disadvantage is the low speed of documentation compared to PLS. Photogrammetric documentation is currently at a very high and fast level in the form of SfM or else IBMR, which produces, similarly to laser scanners, a point cloud [32, 33]. In the case of photogrammetric technology, the point cloud is always textured. It can be said that even photography is a certain form of scanning but using a matrix of detectors and usually in an irregular sequence. It is necessary to add a scale bar or measure at least one distance on the object, because photogrammetry does not work with metric units, but in pixels and lines. The disadvantage of close photogrammetry during this expedition was the strong Sun, common in Morocco. It makes strong shadows, which create an incorrect texture during processing. Even so, documented and mapped objects were often dark interiors, where a flash or special lighting is required. It was not possible to photograph long, irregular, and dark corridors and create a point cloud from the photographs because of both lack of time and appropriate equipment like studio lighting. For this reason, only some objects were documented photogrammetrically like special building details, artifacts etc.  
Figure 7: Schematic workflow for (**a**) personal laser scanner (PLS) ZEB-REVO, (**b**) TLS BLK360, and (**c**) for Image-Based Modeling and Rendering (IBMR) photogrammetry.