# Mobile LiDAR for Scalable Monitoring of Mechanically Stabilized Earth Walls with Smooth Panels
## 5 Experimental Results
### Comparative Analysis of TLS and MLS Serviceability Measures  
The \(\alpha_{L}\) and \(\alpha_{T}\) angular distortions for the MSE wall planar face depicted in Figure 13 and the recommended tolerable values (denoted by the red lines) are illustrated in Figure 19. The angular distortions were assessed using the longitudinal and transversal lines in Figure 13 (i.e., L1 to L9 and T1 to T6 for \(\alpha_{L}\) and \(\alpha_{T}\), respectively). The horizontal line in Figure 19a shows the tolerable \(\alpha_{L}\) (1/200) for a joint width of 19 mm and panel area of 4.5 m\({}^{2}\). The horizontal line in Figure 19b, on the other hand, shows the post-construction tolerable and \(\alpha_{T}\) (1/240), as suggested by AASHTO [6]. Figure 19 shows that both \(\alpha_{L}\) and \(\alpha_{T}\) derived from the MLS are closely similar to those obtained using the TLS point cloud. This similarity confirms the capability of MLS in achieving a reliable, high-quality assessment of standard serviceability measures. As far as the MSE wall evaluation is concerned, Figure 19a,b show that this wall meets the tolerable \(\alpha_{L}\) measure. However, it does not meet the tolerable \(\alpha_{T}\) measure. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**X\({}_{\text{T}}\) (\(\mu\pm mm\))** & **Y\({}_{\text{T}}\) (\(\mu\pm mm\))** & **Z\({}_{\text{T}}\) (\(\mu\pm mm\))** & **\(\Omega\) (deg \(\pm\) sec)** & **\(\Phi\) (deg \(\pm\) sec)** & **K (deg \(\pm\) sec)** & \(\theta\)**- (m)** & **Average Normal Dist. (m)** & **RMSE (m)** \\ \hline  & & & & & (a) & & & \\ \(-0.003\) & 0.023 & 0.002 & \(-0.104\) & \(-0.008\) & 0.014 & & & \\ \(+0.02\) & \(+0.01\) & \(+0.02\) & \(+0.01\) & \(-\pm 0.00\) & \(-\pm 0.00\) & 0.0016 & 0.0012 & 0.0018 \\  & & & &Recently-available, local serviceability measures include the position of the lower left corner of each panel (Xo, Yo, and Zo) and angular orientation of each panel (\(\theta_{xp}\), \(\theta_{yp}\), and \(\theta_{zp}\)) relating the \(P_{cs}\) and \(LF_{cs}\) coordinate systems. Table 2 shows a sample of the calculated values of such performance measures from the TLS and MLS point clouds for the 32 panels covering face 3 along facade 2 of the MSE wall. The \(X\)-coordinate of the origin of the \(P_{cs}\) relative to the \(LF_{cs}\) should be close to zero for a properly constructed MSE wall. Moreover, the \(YZ\)-coordinates of the origin of the \(P_{cs}\) reflect the joint width between the panels and the overall dimensions of the panels. Therefore, panel position, identified through repetitive scans over time, can identify potential relative movements among the panels of a given face. The second set of measures include the angular rotations representing the relationship between the \(LF_{cs}\) and \(P_{cs}\). The angles \(\theta_{yp}\) and \(\theta_{zp}\) define out-of-plane rotations of the panel relative to the \(LF_{cs}\), while \(\theta_{xp}\) signifies a rotation in the plane of the panel. For a well-constructed wall, these rotation angles should be close to zero. The evaluated dimensions of complete/non-occluded panels can be used as a supplementary measure for validating the proposed methodology by evaluating their similarity to previously known panel size. For example, panels 3, 4, 5, and 7 had an estimated width and height varying from 2.95 to 2.97 m and from 1.46 to 1.48 m, respectively, as presented in Table 2. These estimates are quite close to the expected 3 m by 1.5 m panel dimensions. Figure 19: Angular distortions for face 3 along facade 2 of the MSE wall: (**a**) derived longitudinal angular distortion for lines L1–L9 in Figure 13, and (**b**) derived transversal angular distortion for lines T1–T6 in Figure 13 (horizontal lines in a and b represent the tolerable longitudinal and transversal angular distortions, respectively).