UAV application to estimate oil palm trees health using Visible Atmospherically Resistant Index (VARI) (Case study of Cikabayan Research Farm, Bogor City)Medina Nur Anisa, Rokhmatuloh and Revi HerninaE3S Web Conf., 211 (2020) 05001DOI: https://doi.org/10.1051/e3sconf/202021105001