PSI - Issue 54

Francisco Afonso et al. / Procedia Structural Integrity 54 (2024) 553–560 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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The aforementioned photogrammetric system must be attached to the train and still be able to have a direct line of sight to the retaining walls. This attachment procedure should be easy to implement, including the removal phase, without affecting the physical integrity of the train. Thus, a support structure containing four suction cups was designed, allowing the system to be attached to a lateral locomotive window, that can be seen in Fig. 2 alongside a real implementation of the system.

Fig. 2. (a) final support structure; (b) implementation of the system in a locomotive’s lateral window .

The support structure is composed of a group of aluminum profile bars that both support the photogrammetric system and allow a good positioning of the suction cups throughout the window’s surface. 4. Software Custom software was developed in order to control and automate the system, following the operation logic described in Fig. 3. Initially, the computer receives the coordinates of the area of interest, which will be checked against the current GPS coordinates of the locomotive as it moves. As the locomotive approaches the target location, the system starts the acquisition of the retaining wall’s images, saving them to RAM. The aim of this approach is to avoid the time required to save data to disk and thus maximize the frame rate in the short time period during which an acquisition is performed. If either the end of the area of interest is reached, or the RAM reaches 85% usage, the acquisition stops and the software starts the process of saving the images to the disk, in RAW format. As soon as all the images are stored in the disk, the software awaits further indication of another area of interest’s GPS coordinates . In parallel, the stored images become available for post-processing. Both cameras are run independently to maintain the highest possible frame rate for each. These factors, alongside the lens aperture, are essential in creating the best possible environment for a quality acquisition using this system.