## 1 Introduction  
Recent emphasis on serviceability control in geotechnical engineering projects demands accurate measurements of the displacements of structures and the ground surface. Numerous studies have been conducted to analyze the factors affecting the ground deformation during deep excavation, whether in rock or soil [1, 2, 3, 4, 5, 6, 7]. Routine measurements of ground settlements adjacent to a deep excavation project are legally mandated, although only a minimum number of monitoring points are controlled in most projects with tight budgets. Unfortunately, such legal efforts have not successfully prevented a catastrophic collapse, mainly because the location initiating the collapse is often out of the range controlled by the measurement of the monitoring points. The adaptive management technique for ground deformation control including the inverse analysis is also limited because it relies on those monitoring points [8; 9]. Settlement measurements are possible with synthetic-aperture radar (SAR), but images of the area of interest may be insufficient for frequent investigation [10]. Consequently, a technique for measuring the displacements induced by excavation work in the entire range or full field is crucial for ensuring construction safety [11]. Recent developments in computer performance and the increased use of digital photographs have stimulated advances in photogrammetric software. Photogrammetry is a technique for determining the three-dimensional geometry of physical objects by measuring and analyzing their two-dimensional photographs. Terrestrial photography provides detailed dimensional information about an object using images near or on the surface of the earth. In close-range terrestrial photography, the size of the object and the camera-to-object distance are both less than 100 m [12]. Several papers related to close-range photogrammetry have been dedicated to various application fields such as industrial engineering [13], cultural heritage documentation [14; 15; 16; 17; 18], and geomorphology [19; 20; 21; 22; 23]. Close-range terrestrial digital photogrammetry is widely applied in rock mass discontinuity characterization [24]. In civil engineering, close-range photogrammetry plays a vital role in engineering surveys, including as-built documentation of existing facilities and building information modeling. The bridge deformation and health monitoring were measured using the photogrammetry technique [25; 26; 27; 28; 29; 12]. The deformation of concrete tanks and retaining walls under working conditions can be measured using high-precision photogrammetry with high-resolution cameras [30; 31]. Various applications of the close-range terrestrial photogrammetry technique also reveal the possibility of full-field measurements of displacements induced by deep excavation work in urban areas. Pedestrian sidewalks paved with concrete pavement blocks are frequently located adjacent to deep excavation sites. Measuring the displacements of these pavement or paving blocks via close-range photogrammetry can resolve the practical difficulties in investigating the ground deformation induced by deep excavation works in urban areas. We opted to use Unmanned Ground Vehicles (UGVs) as an alternative to Unmanned Aerial Vehicles (UAVs), as the latter often lead to safety and regulatory concerns when operated in urban areas [32; 33; 34; 35; 36]. To the extent of our understanding, the methodology of monitoring the movements of paving blocks through close-range photogrammetry, carried out by cameras affixed to the UGV system, has not been systematically presented. Figure 1 displays the paving blocks adjacent to the excavation site. In Figure 1, the construction site is located behind the wall; moreover, various displacements of paving blocks can be observed. Figure 1: Displacements of paving blocks adjacent to the deep excavation site: (**a**) settlement and non-uniform block pavements; (**b**) uplift; and (**c**) settlement and horizontal displacement.