“There has been a new breakthrough in the field of sag measurement for transmission lines. The traditional sag measurement method is cumbersome and time-consuming to operate, while monocular vision methods are limited by field of view and resolution, making it difficult to cope with the measurement challenges of large-span transmission lines. Researchers have proposed a local photogrammetry method that combines IMU accelerometer sensors and high-resolution industrial monocular cameras to address this issue. Given a small number of transmission line parameters, it is only necessary to capture the left side of the tested conductor. By introducing semantic segmentation technology, the conductor in the image can be extracted, and a photogrammetric model can be established to restore the three-dimensional shape of the conductor and calculate the sag. This method is not only easy to operate, but also has high measurement accuracy, with a relative error controlled within 5%. It provides a new solution for sag measurement of transmission lines and is of great significance for ensuring the stable operation of transmission lines.”