DRONES AS A TOOL FOR TAKING DATA ON FACADES

Abstract

One of the most common pathologies in the service life of single-layer mortar is the loss of adhesion. This leads, in the first instance, to cracking and, subsequently, to the detachment of fragments. During the late 1990s and a good part of the 2000s, this coating was commonly used as a finish for the façades of apartment compounds all over Spain. This widespread use, together with the diverse professional qualifications of construction-related trades, has led to the recurrent appearance of material failures of this nature. Traditionally, data collection on façades has been carried out using mechanical aids, such as scissors or lifting platforms, or by erecting scaffolding. The first options are sometimes not economically viable, while the second involves a disruption to the users of the building, as it must be erected from the initial phase until the project is processed. An alternative to these auxiliary means is offered by image capture systems through photogrammetry, which favor and improve the collection of information, as well as the taking of measurements [1]. In addition, these techniques, particularly those using drones, imply a low cost and rapid execution [2]. The aim of this communication is to show the work carried out using drones equipped with photogrammetric equipment to scan the façade of a residential building in the phase prior to carrying out the restoration project. The methods followed were structured in seven stages: preliminary studies, data collection, scanning process, identification of lesions, post-production of the images, analysis of the results and preparation of the project. The preliminary studies confirmed that the original plans of the building did not exist, so the morphology and location of the building were analyzed from the outside. It could be seen that the affected parts corresponded to the overhangs of the balconies, but the characteristics of the building prevented the lesions from being seen correctly either from the ground or from adjacent buildings. Therefore, instead of resorting to a traditional solution with scaffolding, photogrammetry with drones was chosen for data collection. For the scanning of the façade, more than 20 turns were necessary to cover all the rows of balconies of the building. A technical sheet was drawn up for each balcony, identifying the lesions, classifying the damage and proposing possible interventions to be carried out. The images then had to be processed, as they had to be adjusted to avoid distortions due to lens deformations [3]. The work consisted of transforming the images in such a way that their margin of error was so small that they could be used as a true-to-scale representation and serve as a basis for measurements. After analyzing the results taken from the technical files and the post-produced images, the restoration project for the façade was drawn up and approved by the Madrid College of Architects. The results obtained after the process was completed were satisfactory, as the data taken with the scanning carried out by the drones allowed a customized solution to be designed in accordance with the problem detected. Furthermore, it did not cause any inconvenience to the building's neighbors as no auxiliary equipment had to be installed. The conclusion of this work is that the use of technology in building construction, in this case drones, allows the magnitude of lesion on the façade to be known with sufficient accuracy, reducing the error in the measurements for the applied project to a minimum.