Seabed Object’s Height Estimation Method Utilizing Tilt Angle Changes of Imaging Sonar

Underwater mapping is one of the necessary technologies for underwater exploration. However, when the sonar sensor, widely used to observe the surrounding environment, scans the scene, terrain’s height information can be lost. This paper proposes a method to restore the lost height information by adjusting the tilt of the sonar sensor with the pan-tilt mechanism. The height of the object can be calculated by analyzing the changes of the highlights of the object and the seabed change according to the sonar imaging model in the successive sonar images acquired while changing the tilt angle. The proposed method has been verified through a water tank experiments. The restored height information can be utilized for various underwater operations such as obstacle avoidance of autonomous underwater vehicle and underwater three-dimensional mapping.