## 3 Results
### The Third Test: The [PERSON]'s San Francesco Bridge at Cosenza
Figure 18: A single line scanned: (**a**) The section of the pylon; (**b**) The upper part of the scanned line superimposed to 3D model of the pylon. A comparison between the results obtained by the total station and the acquisitions of the TLS in line scanner mode showed a substantial agreement between the two techniques. Also the comparison with the acquisitions of inclination sensors confirmed the reliability of the methodology. Figure 19 shows some test results. The magnifications correspond to the areas circled in blue in the thumbnails. The point cloud of the profile acquired with the unloaded bridge is in blue. First of all we can see that the precision declared for the instrument and reported in Table 1 is confirmed. The cloud of blue points, in fact, is about 8 mm thick. Therefore the precision of the acquisitions is about ten times lower than the displacements we have to measure. In the panel 19a we can see the displacements of the pylon head. The height, referred to the TLS centre, is about 81 m. The dense red point cloud on the left was obtained during the stop of the first truck. The red dense point clouds on the right were obtained during the short stop of the second truck and during the stop of the third one. At the end of the TLS acquisitions, three trucks were positioned on the bridge. Also this point cloud is 8 mm thick. Scattered points were acquired while the second and third trucks were running. Point clouds acquired during truck slowdown become denser. We observe an overall displacement of 41 mm. The first two mobile loads caused roughly half of the total displacement. In the panel 19b one can see the points acquired in correspondence with the constraint device in which the rods can slide, 69 m above the TLS. In this case, we can see that the horizontal displacements begin with the run of the second truck. The analysis of this behavior is outside the scope of our study. The maximum displacements are slightly lower with respect to the upper part. Since these zones are close together, this behavior seems reasonable. The points acquired in the lowest part of the pylon are shown in panel 19c. The height of this zone is 39 m respect to the TLS center. The displacements reach a maximum value of 26 mm. Using the Matlab code described above, the individual lines from the overall file supplied by the TLS were extracted and a timestamp was associated to each line. The interpolating lines were then determined. \begin{table}
\begin{tabular}{c c} \hline
**Event** & **GPS Time (s)** \\ \hline Start of TLS acquisitions & 1,200,220,888 \\ Start of first Truck & 1,200,221,072 \\ Stop of first Truck & 1,200,221,098 \\ Start of second Truck & 1,200,221,186 \\ Stop of second Truck & 1,200,221,214 \\ Start of third Truck & 1,200,221,243 \\ Stop of third Truck & 1,200,221,268 \\ Stop of TLS acquisitions & 1,200,221,500 \\ \hline \end{tabular}
\end{table} 
Table 4: GPS time for the actions performed during the load test. Figure 19: Enlargements of the point clouds obtained before the load test (blue points) and during the test (red points): (**a**) Upper zone of the pylon (z = 81 m); (**b**) Constraint device in which the rods can slide (z = 69 m); (**c**) lower part of the pylon (z = 39 m). Figure 20 shows a stretch of four splines, obtained for different instants, in the upper zone of the pylon. The coordinates are referred to the center of the instrument, so x is the horizontal distance and z is the difference in height with respect to the center of the TLS. The magenta line (GPS TIME 1200220928) is related to the unloading bridge. The other lines relate to the parking of the first truck (blue line), the parking of the second truck alongside the first one (green line) and the parking of the first three trucks (yellow line). From the data collected it is possible to extract the movements of the pylon, at each height, as a function of time. Figure 21 shows the horizontal movements of the pylon at three different heights.