# Mobile LiDAR for Scalable Monitoring of Mechanically Stabilized Earth Walls with Smooth Panels
## 4 Methodology
### Proposed Framework of the Suggested Methodology
If the RMSE value is greater than the expected noise level in the point cloud data--which is in the range of 1-2 cm for the used MLS in this research--the partitioning is revised. Defining the coordinate systems for the MSE wall face in question (\(LF_{\text{cs}}\)) and the enclosed individual panels (\(P_{\text{cs}}\)) is the next step. These coordinate systems, which are shown in Figure 8, are used for determining both global and local serviceability measures. The \(LF_{\text{cs}}\) is defined by the best-fitting plane through the face in question and the local horizontal/vertical directions at the MSE wall site. More specifically, the \(y\)-axis of the \(LF_{\text{cs}}\) is defined along MSE wall face (as defined by the fitted plane parameters) and is parallel to the horizontal plane of the mapping coordinate system at the study area. The \(z\)-axis of the \(LF_{\text{cs}}\) is established to be parallel to the plumb line at the MSE wall site. Finally, the \(x\)-axis of the \(LF_{\text{cs}}\) is derived to define a right-handed coordinate system. To enable straightforward derivation of the \(LF_{\text{cs}}\), the geo-referencing parameters from the MLS are established in a local mapping coordinate system with the \(z\)-axis pointing in the local level (plumb line) direction at the MSE wall site location. The \(P_{\text{cs}}\) is needed for deriving the panel-to-leveled face differential rotation and translation as well as the panel-to-panel displacement. As can be seen Figure 8, the panel coordinate system is defined with its \(y\)- and \(z\)-axes aligned along the bottom and left sides of the bounding rectangle enclosing the panel in question. Finally, the \(x\)-axis of the \(P_{\text{cs}}\) is derived to define a right-handed coordinate system (i.e., it is defined by the normal to the panel surface). A key prerequisite for a reliable derivation of the local serviceability measures is to ensure that the \(P_{\text{cs}}\) is defined in a similar manner for all the panels within a particular face. For this purpose, this study utilizes a region-growing segmentation procedure to identify the points constituting the individual panels (these points are then used to define the panel coordinate systems by deriving the MBRs that enclose them). For the panel segmentation, the Local Point Spacing (LPS) and normal distance (\(n_{d}\)) from the best-fitting plane to the MSE wall face are used as the region-growing criteria. The fundamental assumption for the segmentation using such criteria is that points with large normal distances from the best-fitting plane correspond to the joints between neighboring panels. The details of MSE wall face partitioning and panel identification are included in Section 4.3. The aforementioned performance measures can be derived once the coordinate systems are defined and the individual panels are isolated from the point cloud along a partitioned face. Section 4.4 describes the derivation of global and local performance measures for MSE walls with smooth panels.