Vegetation monitoring for high voltage transmission and distribution line corridors using satellite stereo images, a case study of Isingiro District.
Mawanda, Tonny Joseph
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Ground inspection is the most common practice around the globe for vegetation management in power line corridors. Unfortunately, this method is costly, it cannot be used in inaccessible areas, it exposes inspectors to harsh environmental conditions, it is time-consuming, stressful and less accurate because it is subject to human judgmental errors. In developed countries, aerial borne inspection methods such as LiDAR technology, helicopter patrols, Synthetic Aperture Radar (SAR), Unmanned Aerial Vehicles (UAV) and aerial videography are being used. These aerial borne methods are quite expensive especially for the relevant authorities in developed countries. In this research a novel approach to vegetation monitoring for high voltage power line corridors using 50 cm spatial resolution Pléiades 1A satellite stereo imagery is described. In particular, Pléiades 1A stereo imagery covering the study area in Isingiro District was used to generate a digital surface model showing the spatial relationship between vegetation and high voltage power lines. Pléiades 1A stereo imagery was then segmented into a chess board grid, processed using texture classification and NDVI threshold values so as to identify tall trees. Using the DSM together with the data layer showing tall trees and that showing the high voltage power line corridors, the degree of vegetation encroachment on high voltage power lines in the study area at the time of image acquisition was determined. It was found that the DSM generated was accurate to 17.3 cm RMSE. This demonstrates the capability of stereoscopic techniques using Pléiades 1A`data in modelling the spatial relationship between vegetation and high voltage power lines in our study area. An unnamed line denoted by code 4 had a considerable amount of its tree canopy within its growth limit zone and this was further confirmed through site visits. Therefore, monitoring power line corridors using satellite stereoscopy is a suitable complement to ground inspection methods. Keywords: Vegetation monitoring, satellite stereo imagery, power line corridors, satellite stereoscopy, stereoscopic vision