EXTRACTION OF DEBILITATED TREES ALONG THE ROAD BY BLOCKED NDVI

Abstract. A method for extracting degraded trees was developed by using a near-infrared camera modified from a digital camera to photograph roadside trees. Traditionally, remote sensing has utilized vegetation index using near-infrared and red bands as a method to extract degraded trees. However, it was not possible to assess the health of roadside trees sufficiently because the observation from above only observed the canopy of the roadside trees. Observations from the ground can cover the shortcomings because they observe the sides as well as the canopy of the tree. However, ground-based observations are strongly influenced by sunlight, which needs to be compensated for. Also, since the target is trees on the side of the road, it is desirable to take a video of the trees from above the vehicle. The basic idea of this study is simple: a tree where the vegetation index is lower than other trees is considered a cautionary tree, and a tree where the vegetation index changes over time or month is lower than other trees is extracted as a degraded tree. In order to compare videos shot at different times, frame matching of videos and geometric correction between frames were performed. To account for geometric accuracy, pixels were grouped together as blocks, and changes in vegetation indices from block to block were analyzed. In order to improve the accuracy of the analysis, non-vegetation areas were removed from the images. As a result, blocks of debilitated trees were extracted from the trees along the road.