中文摘要：

输电线路的弧垂和对地距离是线路设计和运行的主要指标，其准确测量对线路的运行安全具有极其重要的意义。结合图像处理和摄影测量技术，提出一种新的输电线路弧垂测量方法。根据无人机载数据采集系统针对同一段输电线路，在不同拍摄位置和角度拍摄传回的多张现场照片，利用平滑滤波、边缘检测和边界追踪相结合的图像分割算法识别出照片中弧垂特征点，并利用立体像对前方交会算法推导对应弧垂点的实际坐标值，进而实现对输电线路弧垂和对地距离的准确测量。与现场激光测距仪实测结果相比较，新测量方法平均误差率〈1．3％，最大误差率〈2．8％，证明该方法正确有效，满足实际应用的需要。

英文摘要：

Accurate calculation of the distance between sag of transmission line and ground is especially important. We proposed a method to calculate the sag of the transmission line by photogram metric technology, which could ac curately locate the sag of the transmission line according to process the images sent from the data acquisition system on a UAV. Smooth filtering, edge detection and tracking boundary were mainly used to process the photos from work field and to identify the features of the sag. Then, the actual coordinates of the image related to the features could be calculated by the method of coordinate transformation and the stereo image to forward intersection in photographing measurement technique. Finally, the accurate data of the distance between the sag of the transmission line and the ground were got. The mean error of the new method to calculate the sag of the transmission line was about 1.3 % and the maximal error was 2.8 % in comparison with the results of laser distance measuring instrument. Field test results show that this way is fast and accurate, has strong anti noise ability, and meets the requirements of application in work field.