Seasonal and Diurnal Change of NDVI from UAV Imagery in Clear Day Condition

Abstract

Recent advanced UAV (Unmanned Aerial Vehicle) technology supply new opportunities for estimating crop condition using high resolution imagery. The objective of this study was to analyze the change of vegetation index in UAV imagery according to sun altitude. This study was conducted using a fixed-wing UAV, called Ebee, with Cannon S110 camera from November 2017 to September 2018 in the grass experiment of National Institute of Agricultural Sciences on a clear day. As a result, the NDVI (Normalized Difference Vegetation Index) of UAV imagery decreased after 9 a.m. and showed a minimum value at 13 a.m. and increased since then. The solar zenith angle and the NDVI of UAV imagery showed a positive linear relationship. Therefore, in order to quantitatively compare and analyze the time series vegetation index, it is necessary to establish a UAV flight plan considering the change of solar zenith angle. It is thought that it will be necessary to examine cloudy days with various crop in the future.