Abstract: A method includes measuring a radius of curvature at each of the plurality of positions of the outer peripheral surface of the predetermined section of the pipe is measured through the first device. A second device is detachably coupled to the plurality of positions along the outer peripheral surface of the predetermined section of the pipe. A wall thickness at each of the plurality of positions of the outer peripheral surface of the predetermined section of the pipe is measured through the second device. A cross-sectional area of the predetermined section of the pipe is measured based on a measurement data including the radius of curvature and wall thickness at each of the plurality of positions of the outer peripheral surface of the predetermined section of the pipe.