Powerline inspection is a critical maintenance task that was performed by helicopters or, more recently, by manually piloted drones, both without automation or any real-time awareness of data completeness. Autonomous UAVs with advanced sensors have the potential to overcome these issues, but real-time mapping and autonomous navigation in complex outdoor environments remain challenging. Fraunhofer Italia aims to address these challenges by developing a UAV and ground station system to support maintenance teams in real-time infrastructure inspection, with a focus on powerlines. This thesis, in collaboration with Fraunhofer Italia, proposes a perception framework for geo-referenced 3D point cloud mapping using stereo vision and high-precision GNSS.