Environmental monitoring is a critical issue for comprehending climate impact on natural and agricultural systems, understanding hydrological processes, optimizing water resources, and preventing natural disasters. Nowadays, most of available data is obtained with ground-based measurements or remote sensing that provide limited information in terms of spatial extent or resolution (temporal or spatial). In this context, one of the greatest potential in environmental monitoring is represented by the use of Unmanned Aerial Systems (UASs) whose application and use is rapidly growing in the scientific community. These devices offer an extraordinary opportunity to fill the existing gap between remote sensing and field measurements providing high resolution measurements over wide areas and at high frequency. UASs allow to extend and improve the description of river basin hydrology, agricultural systems and natural ecosystems affording an impressive level of detail. Several new UAS-based approaches have been recently introduced to monitor soil water content, vegetation state, river evolution and stream flow during low-flow and floods. Such measurement practices, algorithms and data assimilation techniques should be harmonized in order to enhance our ability to monitor the environment. The Action will co-ordinate efforts to address these issues, by establishing harmonized monitoring practices, enhancing the use of observations by promoting new monitoring strategies, bringing together different communities, facilitating data transfer, upgrading and enlarging knowledge through networking, exchange and training, and linking them to activities in international agencies and global networks.
