Drones are used to take on a wide variety of surveillance tasks. In certain cases, they will need to perch on inclined surfaces to continue monitoring while saving battery. This video from ARPL NYU shows an active visual perching control system for drones that enables them to land on inclined surfaces up to 90 degrees. As they explain, this system:
generates dynamically feasible trajectories to navigate and perch on the desired target location while taking into account actuator and Field of View (FoV) constraints. By replanning in mid-flight, we take advantage of more accurate target localization increasing the perching maneuver’s robustness to target localization or control errors.