This paper describes a method of azimuth angle estimation using RTK-GNSS and gyroscope on a small unmanned aerial vehicle (UAV). Recently, a power line and steel tower inspection using UAV is attracted at electric power companies. However, azimuth angle cannot be estimated due to the high magnetic field in the vicinity of the power line. We propose a method to estimate azimuth angle by combining RTK-GNSS and gyroscope with Kalman filter. As a result, the proposal method has the same azimuth angle estimation accuracy as the method using the magnetic sensor in the static test. In the high magnetic field environment, the proposed method could stably estimate the azimuth angle. We implemented an autonomous flight test with a UAV incorporating our proposed method. As a result, even during the flight, the proposed method was able to estimate the azimuth angle equivalent to that using a magnetic sensor.
