Abstract: The present invention relates to compounds of formula (I), wherein R1 to R3, A1 to A3 and n are as described herein, and their pharmaceutically acceptable salt thereof, and compositions including the compounds and methods of using the compounds.

Abstract: A system and method for measuring an image distance of power transmission lines with an unmanned aerial vehicle (UAV). The system includes: a UAV, a master console, and a plurality of cameras. The cameras are configured to collect 2D image data of a power transmission line corridor. The UAV includes a vehicle body, a lidar device, a rotor assembly, a power unit, a flight control processor, a state detection device, and a wireless communication module. The lidar device is configured to collect 3D point cloud data of the power transmission lines. The master console is configured to receive the 2D image data and the 3D point cloud data, and establish a mapping relationship between the 2D image data and the 3D point cloud data; recognize a target object, determine 3D point coordinates of the target object, and calculate a distance from the target object to the power transmission lines.