Unmanned Aerial Vehicles (UAVs) are used to detect changes in building façades
In recent years, drones have become increasingly popular not only with professional and amateur filmmakers but also with researchers. A team of researchers from various Lithuanian universities, including Rytis Maskeliūnas from the Kaunas University of Technology (KTU), have used UAV technology to detect changes in building façades against a crowded city background.
Digitized Cities and Digital Twins
With the emergence of digitized cities and digital twins, it has become possible to observe the various changes in buildings, both external and internal. However, outdoor image processing can be difficult in typical European metropolitan areas due to various obstructions to perspectives such as wires, overhangs, poles, and other parts of a building as well as dynamically changing weather conditions affecting the quality of UAV imagery.
Study of Façades in Vilnius Old Town
The team of researchers chose to study the façades of buildings in Vilnius Old Town and surrounding areas. "Vilnius is a very unique place architecturally. The city's Old Town is a UNESCO World Heritage Site and is full of buildings that vary in style, from Gothic church spires to state-of-the-art glass structures," says Andrius Katkevičius, professor at the Department of Electronic Systems, Vilnius Gediminas Technical University. This diversity in architectural styles presented a challenge for the team and motivated them to investigate whether algorithms would be able to work across such a wide range of styles.
Smart Signal Processing Solutions Based on Artificial Intelligence
Such a challenge, according to Maskeliūnas, requires the use of smart signal processing solutions based on artificial intelligence to detect, identify, and classify buildings in the overall background of the city. "The façade is the identity of the building, the architectural face that allows the building to be assigned to one or another category or style. Imagine if suddenly part of the façade of an old building in the Old Town was glazed or redecorated in some avant-garde manner. A drone flying by would record such a change—perhaps it is illegal construction or urban blight," says Darius Plonis, professor at the Department of Electronic Systems, Vilnius Gediminas Technical University.
Drone Assessment of Technical Condition of Buildings
As the drone flies through the city and photographs building façades, the data is sent wirelessly to a computing platform that can determine what class of façade a particular building belongs to. Maskeliūnas believes that the drone's photographs of the façade could also be used to assess the technical condition of buildings: "Water penetration through seams, cracks in the decor or structure, discoloration of façade elements or potentially even dents in the surfaces—all these determine the classification of a building and could potentially allow for a fairly accurate and automated assessment."
An Overcrowded City is a Challenge
According to the researchers, the study aims to detect the boundaries of a building's façade in the face of changing weather and light conditions and to determine its actual style based on façade taxonomy. The complexity of the task depends on the shape of the building's façade, the natural conditions, and the urban background behind it. "For the algorithm, a congested city is the most difficult task to extract useful information, as buildings in city centers or old towns are usually closely packed together," says Maskeliūnas.
Journal Information: Rytis Maskeliūnas et al, Building Façade Style Classification from UAV Imagery Using a Pareto-Optimized Deep Learning Network, Electronics (2022). DOI: 10.3390/electronics11213450