Mobile Application to Support Facade Renovation

We present a mobile application that enables end users to quickly calculate the size of a building facade. Our goal is to support the renovation of facades, as their costs are mainly determined by the surface area. We developed an image-based approach that consists of four steps. First, we measure the facade width using augmented reality (AR) functionalities of modern smartphones. In our evaluation, this measurement achieves an average accuracy of 98.5 %. In the second step, the user takes a photo of the facade and marks its contours. All information is transferred to a server that rectifies the photo. The result of step three is a distortion-free orthophoto of the facade, with the correct ratio of width to height. The fourth and final step is AI-based image recognition to identify facade elements such as windows, doors, and roofs. The facade area is calculated by subtracting the area of facade elements from the total area. We evaluated our application on ten different buildings and achieved an average accuracy of 97.5 % for the facade area.