Vegetation mapping and monitoring by unmanned aerial systems (UAS)—current state and perspectives

Unmanned aerial systems (UASs) represent an important tool to characterize vegetation patterns and processes. Their ultrahigh resolution and flexibility may help to bridge the gap between field and satellite remote sensing data. UASs can address a variety of fields, ranging from biodiversity mapping and monitoring through the assessment of ecosystem structure, plant phenology, and plant stress up to the dynamic processes of natural disturbances and insect outbreaks. There are a variety of sensors, platforms, and procedures available to collect and process UAS data. Therefore it is necessary to optimize survey workflows in a direction to capitalize on the great advantages of technology, ultrahigh spatial and potentially also temporal resolution. Here, an overview of the methods applied in ecosystem studies are provided to better illustrate different workflows for monitoring vegetation state, structure, status, and dynamics and introduce challenges and future perspectives.