Patent attributes
A positional sensor detects a current position of a boat body and outputs position information indicating the current position. A controller receives the position information. The controller determines a target position of the boat body. The controller calculates the distance between the current position and the target position. The controller determines a target speed of the boat body to reach the target position in accordance with the distance. The controller calculates the force of an outside disturbance. The controller determines a target propulsion force of a propulsion device based on the force of the outside disturbance and the target speed. The controller generates an instruction signal to control the propulsion device to produce the target propulsion force.