Actual measurements Antennas Conventional methods Digital elevation model Elaeis Forestry GIS Ground sampling distances Image segmentation Oil palm Palm oil Seed generations Seeded region growing Segmentation methods Surveying System of third-order boundary value problem Tree crown delineation Unmanned Aerial Vehicle (UAV) Unmanned aerial vehicles (UAV) accuracy accuracy assessment block method canopy architecture diameter digital elevation model height multiple shooting technique orthophoto segmentation tree