Comparison of visual vitality assessment and NDVI calculated using a UAV platform for cherry trees

Abstract

Trees play an important role in urban greening, but there are often problems with their growth, so it is necessary to monitor their growth status as basic information for appropriate tree management. The aim of this study was to analyze the relationship between the results of visual surveys of tree vitality, which are widely used as a method of monitoring tree growth, and vegetation indices obtained using UAV platforms, and to verify the effectiveness of these methods as a monitoring method for tree growth. The study focused on cherry trees planted in Yahagi Ryokuchi Hiradobashi Park (Toyota City, Aichi Prefecture). The relationship between NDVI calculated using UAV platforms and the evaluation rank of visual surveys of tree vitality was analyzed. It was found that NDVI could be used to evaluate tree health and leaf volume, and that a buffer of 1.5 m was the most suitable spatial unit for aggregating NDVI values. This study has clarified the effectiveness of NDVI for each category of vitality survey. In the future, by applying the methods of this study to various cases, it is thought that knowledge will accumulate and the methods will develop into more versatile methods, and it is hoped that this will contribute to the appropriate management of cherry trees.