Automatic block generation and 3D line extraction in photogrammetric power line inspection

We develop a photogrammetric power line inspection system. Its main objective is to monitor the relative distance between high voltage power line and around objects, and alert if the warning threshold is exceeded. Our photogrammetric power line inspection system generates DSM of the power line passage, which comprises ground surface and ground objects, for example trees and houses, etc. In order to reveal the dangerous regions, where ground objects are too close to the power line, 3D power line information should be extracted at the same time. In order to improve the automation level of extraction, reduce labour costs and human errors, an automatic pole tower and spacer numbering method is proposed. The pole tower automatic numbering is in accordance with GPS position data of the image having pole tower projection, finds the pole tower whose measurement position is closest to it, and the found pole tower´s code number is set to pole tower projection. Then a block can be defined by a start pole tower and an end pole tower. The spacer automatic numbering process is limited within a block, and it can be achieved by using epipolar constraint after an aerial triangulation bundle adjustment. The flight experiment result shows the proposed method can give correct code number to pole towers and spacers, and the proper 3D power line information can be obtained by space intersection using found homologous projections.