# Monitoring and Data Analysis in Small-Scale Landslide Physical Model
## 3 Review of Landslide Monitoring Equipment
### Geodetic Monitoring System in Small-Scale Landslide Modeling
#### 3.1.2 Terrestrial Laser Scanner (TLS) and Structure-from-Motion (SfM) Photogrammetry  
Terrestrial laser scanner (TLS) used to capture model surface is the FARO Focus 3D X 130 (FARO Technologies Inc., Lake Mary, FL, USA) shown in Figure 4a. Similar laser scanner, a Leica ScanStation 2, was used by [PERSON] et al. [44] in laboratory experiments to capture deformation of loess slope surface. FARO Focus 3D X 130 is a high-speed three-dimensional terrestrial laser scanner for detailed measurement and documentation. Single-point measurements are repeated up to 976,000 points in a second; therefore, the resulting images are an accumulation of millions of 3D measurement points. Main features of the laser scanner are: high accuracy, high resolution, high speed, intuitive control via the built-in touchscreen display, high mobility due to its small size, light weight and integrated quick charge battery, WLAN for remote control, integrated dual axis compensator to automatically level the captured scan data, integrated GPS sensor to determine the position of the scanner, integrated compass and altimeter for orientation and height information of the scans, and 3D color scans because of the integrated color camera with a resolution of 70 megapixel. Technical specifications of the laser scanner are stated in Table 5[58]. \begin{table}
\begin{tabular}{c c c c c} \hline
**ARAMIS** & **Frame Rate** & **Resolution** & **Measuring Area** & **Calibration Objects 1** \\
**System** & & & & \\ \hline \multirow{2}{*}{4 M} & 168 fps & 2400 \(\times\) 1728 pixels & From 125 \(\times\) 90 mm\({}^{2}\) to & Calibration object from \\  & 1300 fps & 2400 \(\times\) 168 pixels & 2150 \(\times\) 1600 mm\({}^{2}\) & 350 \(\times\) 260 mm\({}^{2}\) \\ \hline \multirow{2}{*}{12 M} & 25 fps & 4096 \(\times\) 3000 pixels (full resolution) & & \\  & 75 fps & 4096 \(\times\) 1000 pixels (1/3 of image) & From 20 \(\times\) 15 mm\({}^{2}\) to & Calibration cross from \\  & 100 fps & Reduced resolution (binning) & 5000 \(\times\) 4000 mm\({}^{2}\) & 1750 \(\times\) 1300 mm\({}^{2}\) to \\ \hline \end{tabular} \({}^{1}\) Calibration objects are suitable for both camera systems.  
\end{table} 
Table 4: Characteristics of the ARAMIS GOM high-speed camera systems. Figure 3: Both sets of high-speed cameras—ARAMIS 4 M (up) and ARAMIS 12 M (down). The Focus TLS works by sending an infrared laser beam into the center of its rotating mirror. The mirror deflects the laser beam on a vertical rotation around the environment being scanned; scattered light from surrounding objects is then reflected back into the scanner. Scanner uses phase-shift technology to measure distance where constant waves of infrared light of varying length are projected outward from the scanner. Upon contact with an object, they are reflected back to the scanner. The distance from the scanner to the object is accurately determined by measuring the phase shifts in the waves of the infrared light. The \(x\), \(y\), and \(z\) coordinates of each point are then calculated by using angle encoders to measure mirror rotation and the horizontal rotation. These angles are encoded simultaneously with the distance measurement. Distance, vertical angle, and horizontal angle make up a polar coordinate (\(\delta,\ \alpha,\ \beta\)), which is then transformed to Cartesian coordinates (\(x,y,z\)). The scanner covers a \(360^{\circ}\times 300^{\circ}\) field of view (horizontal \(\times\) vertical) [58]. The laser scanner does the measurement in two steps: first one being the measurement of geometry and defining of \(x\), \(y\), and \(z\) coordinates, and the second one is the photographing process for determination of colors. Colors are determined by the red/green/blue (RGB) scheme where each pixel consists of a certain combination of red, green, and blue light (from 0 to 255) which in return give a certain color depending on the strength of each color.