Appropriate vegetation indices and data analysis methods for orchards monitoring using UAV-based remote sensing: A comprehensive research

• UAV-based remote sensing in orchards monitoring is demanding. • In this field, more than seventy types of vegetation indicators have been used so far. • In Asia and Europe, more than 75 % of those have been performed. • The used vegetation indices and analysis methods were descriptively analyzed. • Appropriate vegetation indices and analysis methods were separately nominated. Orchards monitoring is indispensable to various assessments and evaluations that are usually associated with unmanned aerial vehicle (UAV)-based remote sensing , high-tech sensors, indices and data analysis methods. Apart from physical platforms to know, use and develop such systems, essential knowledge includes data analysis methods and indices. Over the last decade, much research has been performed in orchards monitoring by UAV-based remote sensing, while no comprehensive research has been done for different data analysis methods and the numerous vegetation indices. In this research, various topics have extensively been studied including subjected countries and orchard trees, used platforms and cameras. Nonetheless, the main focuses of the comprehensive research have been on the extracted features, appropriate vegetation indices, and data analysis methods for orchard trees monitoring using UAV-based remote sensing. In detail, the key items were also characterized and analyzed. Lastly, some notable data, applicable extracted quantitative and qualitative outcomes, current challenges and horizon of future possibilities on the topic were revealed.