Corridor mapping has a number of applications. One of these is powerline inspection. Power companies in Australia (and many other countries) are required to maintain a regulated clearance space around all powerlines for bushfire mitigation and safety purposes. Current methods for checking clearances involve laborious, ground based, manual visual inspection of distribution networks to determine which trees must be cleared, together with extensive aerial audits of the network to ensure effective clearance of the network prior to the bushfire season. These are expensive, time consuming and subject to observer bias or a failure to observe trouble spots at the right time.
For several years, Powercor Australia Ltd, the largest electricity distributor in the Australian state of Victoria, has been interested in the possibility of developing a cost effective airborne image capture and processing system to automatically measure the clearance of trees from powerlines to support bushfire mitigation operations. It is envisaged that such a system will involve an aircraft flying at approximately 80 metres above the ground, mounted with forward looking cameras beneath the tip of each wing, that capture a continuous series of images of the powerline infrastructure. The system will also carry differential global positioning systems (GPS) and inertial navigation systems (INS) to provide position and orientation data for the aircraft.
Powercor came to CSIRO scientists from the Quantitative Imaging Team of CSIRO to carry out several studies to develop a cost effective airborne image capture and processing system to automatically measure the clearance of trees from powerlines. Using stereo vision techniques, the CSIRO developed a software post-processing system that automatically creates three-dimensional (3D) space from the images. Then, after extracting key features from the images (e.g. power poles and powerlines), it measures and reports on the offset of the trees from the powerlines.
The following are examples showing the input images and output digital surface model, orthoimages, and 3D visualisations.
Corridor Mapping – An Opportunity
This technology has the potential to be applied in the mapping and positioning of linear and other features such as roads, railways, pipelines, fibre optic cables, streams and rivers, and, on a large scale, valley systems and shorelines. It could also be used for inventory updating , and geohazard and slope stability assessment of roads and railways. An opportunity exists for an enterprising company to develop a corridor mapping service for asset monitoring.
C. Sun, R. Jones, H. Talbot, X. Wu, K. Cheong, R. Beare, M.J. Buckley, and M. Berman, Measuring the Distance of Vegetation from Powerlines Using Stereo Vision. ISPRS Journal of Photogrammetry and Remote Sensing, 60(4):269-283, June 2006.