UAS based remote sensing for rapid large-scale mapping of urbanized territories for sustainable urban planning: the case of Burgas and Stara Zagora, Bulgaria

According to UN DESA (United Nations Department of Economic and Social Affairs) urban population will become 66 percent of the planet's population by 20501. Unmanned Aerial Vehicles (UAVs) are confirmed as rapid, efficient, lowcost and flexible acquisition systems for remote sensing data with high-resolution and accuracy (sub-meter to few centimeters)2. The urban environment observed at large scale is dynamic and ever changing due to the human activities, which is a real opportunity for UAV and its urban applications such as management of urban infrastructure3 building observation4, urban land cover classification using airborne LiDAR5 and automatic feature extraction for UAV-based cadastral mapping6. A typical photogrammetric UAV workflow consists of flight planning, image acquisition, camera calibration, image orientation and data processing, which can result in Digital Surface Models (DSMs), orthoimages and point clouds7. In this paper, we perform a rapid, multi UAV data acquisition on the territory Bulgarian city of Stara zagora for a single day. 3 fixed-wing UAV, model eBeeX, manufactured by the company AgEagle Aerial Systems, was used in the present survey. The urban mapping area covered by the drones is 31.215 km2. To gather the necessary information, the platform is equipped with a dedicated integrated photogrammetric sensor S.O.D.A with RTK functionality. All the imagery captured by the three drones are postprocessed in Pix4D Mapper v4.8. Highly accurate 3D point cloud, digital surface model (DSM) and high-resolution and accuracy orthophoto map are produced. The results obtained by the drones have a spatial resolution of 5cm per pixel and vertical accuracy between 5 – 10 cm. All the results are exported and published in easy-to-use formats.