The drone‐based inspection process on power transmission lines needs to be automated due to the large scale of power facilities and the limited line of sight available to drone pilots. Through the task environment analysis, however, it was found that the steel tower structure and energized AC power conductors may cause GPS signal distortion and magnetic interference with a drone's geomagnetic sensor, respectively. These factors could seriously affect the drone's autopilot flight, at worst leading to a crash. To enable drone inspections to be performed in a safe and efficient manner, this paper presents the entire process of operating an autopilot inspection drone on the basis of GPS and GIS information in a hazardous ultrahigh voltage environment, and its application results in the field. This process includes how to measure GPS co‐ordinates of steel towers and how to generate an autopilot flight path. More specifically, the paper examines the potential problems that may occur when drones are applied to areas located in mountains and rivers where humans cannot inspect power lines due to a lack of accessibility, and proposes effective solutions to these practical issues.