## 2 Related Work
Landslides happen also inside residential areas causing cracks to buildings and drainage, for example, the study area located in a Malaysian city. Here, to monitor an active landslide, researchers used MLS to assess the movements of the land, in both vehicle-based and human-based mode in a complementary way to acquire completely the surface of the study area [14]. Mobile mapping solutions have been also applied in change detection and deformation analysis for sandy dunes and river courses. The adoption of MLS was illustrated by [PERSON] et al. [15] that provides an accurate and robust method to obtain high resolution space-time datasets along a Dutch beachuseful to understand the changes of dunes volume, under the influence of both marine and aeolian processes. The MLS was carried out mounting the device on a car and using airborne LiDAR to process several DEMs of the sandy dunes. The monitoring of beach dunes is needed to improve the scientific observation of their dynamics. A test was realized in Cap Ferret, France, where researchers combined MLS with aerial photogrammetry to deliver accurate 3D reconstruction of the dunes. They confirmed the good results of using mobile mapping devices for their high level of detail and greater spatial coverage [16]. The best results were also achieved in monitoring the lagoon area of Padre Island National Seashore, located in Texas, where mobile scanning devices may be preferred for the detailed and comprehensive final DEMs useful to detect 3D terrain features and so to monitor geomorphic changes [17]. These challenging trials prove that a mobile LiDAR system, in recent years, has emerged as a viable alternative for surveying coastal beaches and foredunes, but also for riverine topography. Measurements were conducted by [PERSON] et al. [18] using an MMS mounted on a boat and mounted on a manually-operated cart to define the riverine topography and modeling in 3D of the coarse fluvial sediment along the river Tenojoki, in Finland. The application of a MMS was tested by [PERSON] et al. [19] for a complex relief and the following reconstruction of fluvial surface sedimentology and topography of river Feshie, in Scotland. Monitoring actions also occur to control the actual state of civil infrastructures, for example, the maintenance of pavement condition of roads to detect instabilities and to assure safe conditions. It is possible to detect the road surface on 3D models derived from a dense point cloud acquired by MLS. LiDAR instruments are suitable to collect data with adequate accuracy and high resolution for mapping and inventory purposes, and, also, the surveyors can make surveys safely with minimal interruptions of the traffic flow [9]. The use of accurate and dense point cloud data along a route corridor enables the detection of surface distortion, joints, cracks and other roughness conditions [20]. Also retaining walls along roads needs to be monitored to assess their stability, especially in mountainous regions to support either roads or slopes adjacent to roads. An efficient method was proposed by [PERSON] et al. [21] based on a mobile mapping system to detect a retaining wall used to construct a highway, in Austria. The MMS, mounted on a car, generated a high-density point cloud where tilt changes of the structure can be calculated to define the current state of the structure itself. The 3D model helped to recognize forms of damage and their distribution on the surface of the wall, thus compensating for the typical punctual analysis carried out with the total station. Moreover, referring to the case study presented in that article, among the monitored infrastructures they also include water reservoirs and hydroelectric power plants. A boat-based MMS was selected by Brazilian researchers to scan the progression of marginal erosion in different reservoirs of hydroelectric plants. The processed point clouds and rendered meshes and the creation of cross-sections were used to compute the rate and the dynamics of the erosion phenomenon [6; 22].