Camera sightline pointing requirements for aerial inspection of overhead power lines

This paper considers the image quality requirements for video inspection of overhead power distribution lines from a helicopter. The use of video surv eillance techniques for routine inspection of overhead lines is seen as a m eans of automating the process as well as improving the depth and coverage by provision of permanent visual records. One of the principal difficulties of remote video surveillance from a helicopter is the degradation of the i mage due to the motion of the camera sightline. The work reported here intr oduces simulated motion blur onto sharp images to show that the tolerable m otion is of the order of 1-2% of the field of view for static images. An ex pression is obtained for the maximum allowable amplitude of (sinusoidal) si ghtline perturbation for a given value of image blur. The results of an exp erimental assessment of the quality of images subject to sightline motion a re presented and it is shown that the tolerable motion for dynamic viewing is similar to that for static images. It is concluded that optical stabilis ation of the order of 100 mur is necessary for satisfactory inspection deta il. (C) 2001 Elsevier Science B.V. All rights reserved.