  The application of autonomous robots in agriculture is gaining increasing
popularity thanks to the high impact it may have on food security,
sustainability, resource use efficiency, reduction of chemical treatments, and
the optimization of human effort and yield. With this vision, the Flourish
research project aimed to develop an adaptable robotic solution for precision
farming that combines the aerial survey capabilities of small autonomous
unmanned aerial vehicles (UAVs) with targeted intervention performed by
multi-purpose unmanned ground vehicles (UGVs). This paper presents an overview
of the scientific and technological advances and outcomes obtained in the
project. We introduce multi-spectral perception algorithms and aerial and
ground-based systems developed for monitoring crop density, weed pressure, crop
nitrogen nutrition status, and to accurately classify and locate weeds. We then
introduce the navigation and mapping systems tailored to our robots in the
agricultural environment, as well as the modules for collaborative mapping. We
finally present the ground intervention hardware, software solutions, and
interfaces we implemented and tested in different field conditions and with
different crops. We describe a real use case in which a UAV collaborates with a
UGV to monitor the field and to perform selective spraying without human
intervention.
