The camera calibration in monocular vision represents the relationship between the pixels' units which is obtained from a camera and the object in the real world. As an essential procedure, camera calibration calculates the three-dimensional geometric information from the captured two-dimensional images. Therefore, a modified camera calibration method based on polynomial regression is proposed to simplify. In this method, a parameter vector is obtained by pixel coordinates of obstacles and

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... sponding distance values using polynomial regression. The set of parameter's vectors can measure the distance between the camera and the ground object in the field of vision under the camera's posture and position. The experimental results show that the lowest accuracy of this focal length calibration method for measurement is 97.09%, and the average accuracy was 99.02%.