How crop mapping works
Healthy leaves reflect near-infrared light strongly and absorb red light. A camera that records both can compute a vegetation index such as NDVI, which turns a field into a map of plant vigour. Drones give very detailed pictures on demand. Satellites cover large areas on a regular schedule, and some public satellite imagery, such as the European Sentinel-2 programme, is free to use.
From map to action
A map is only useful if it changes what the farmer does. With variable-rate application, a sprayer or spreader adjusts the dose as it crosses the field. With spot spraying, only the affected patches are treated. Soil probes, weather data and yield records are added to explain why one patch differs from another.
Limits to keep in mind
Drone flying and crop spraying are regulated, and the rules differ by country, so operators must check the aviation and pesticide rules where they work. Imagery can be misread without someone who knows the crop, and the benefits depend on the farm, the crop and the season.
Where it is used
- Scouting Finding stressed or weak areas of a crop early, before they spread.
- Variable-rate application Giving each part of a field the seed, fertiliser or spray it needs.
- Irrigation planning Seeing which areas are dry and which are not.
- Record keeping Showing what was applied where, and what happened next.
Drones compared with satellites
Drones give very detailed images on the day you choose, but cover a limited area per flight and depend on the weather and on flying rules. Satellites cover whole regions on a regular schedule, and some imagery is free, but pictures are coarser and clouds can block them.
Many farms use satellite maps to decide where to look, and a drone to look closely.
Key terms
- NDVI
- A vegetation index computed from near-infrared and red light.
- Variable-rate application
- Changing the amount of seed, fertiliser or spray as a machine crosses a field.
- Multispectral camera
- A camera that records several bands of light, including ones people cannot see.
- Ground sampling distance
- The size of the ground area that one image pixel covers.
Common questions
Do drones replace tractors?
- Not usually. They scout, map and in some places spray small areas, while tractors still do most heavy field work.
What does NDVI measure?
- It compares near-infrared and red light reflected by plants to estimate how green and vigorous the vegetation is.
Is precision farming only for large farms?
- Large farms adopted it first, but imagery services and sensors have become available to smaller farms, often as a service.
Sources and further reading
Independent pages we checked while writing this guide. They are not Reinnder products, and Reinnder is not affiliated with them.
Reinnder’s angle
How Reinnder looks at precision farming from the air
Reinnder Agritech is the planned home for drones, probes and models that tell growers what each part of a field needs.
This guide explains the technology in general terms. It is not advice, and it does not describe a Reinnder product on sale.