Aiming at the problem that the height and pitch angle are difficult to measure during monocular ranging

a method for calibrating camera height and pitch angle is proposed

and a water-surface target ranging method based on monocular vision is proposed

and the factors affecting the ranging precision are analyzed.Through camera calibration

obtain the external coordinate of the grid coordinate system on the calibration plate that is coplanar with the water surface to the camera coordinate system

calculate the camera height and the pitch angle. The area of the target on water surface in the image is identified

the maximum value of the ordinate of the pixel in the area

and the average value of the corresponding horizontal coordinate are calculated

and the combined coordinate is taken as the pixel coordinate of the observation point. According to the camera internal reference

perspective projection relationship and rigid body transformation

the three-dimensional information of the observation point in the coordinate system of the unmanned boat is obtained

and then the distance of the observation point is calculated. The correctness and effectiveness of the proposed method are verified by experiments.