New Scientist reports: [edited]
A drone zipping over fields in Denmark can spot the tiny colour variations that give away the presence of weeds in amongst the crops. Logging the coordinates, it can then send a ground vehicle in to spray the densest patches, reducing the need to spray whole fields.
This is the ASETA project, led by Anders La Cour-Harbo of Aalborg University in Denmark. It aims to reduce herbicide use by concentrating weedkiller only in places where it is needed most.
The project uses a camera attached to a UAV to survey the fields. The camera is tuned to pick up parts of the light spectrum that correspond to the reflective signatures of the weeds and crops it is looking for – for example, thistle sticks out because it absorbs yellow light more than surrounding beet plants. Information is sent back to a central computer, where it is used to update previous flight maps of the fields.
The system then identifies areas that could be dense with weeds, and sends the ground vehicle in for a closer look and possible spraying. It's all automatic: the only human input is defining the boundaries of the field to be surveyed. The drone system is currently being trialled in Denmark.