Multispectral satellite imaging, including IR, has existed for many years, but more recently advances in drone technology have enabled photographers, film-makers and scientists to obtain aerial views of subjects such as crops or archaeological sites. There are now many different types available at all price brackets, capable of being fitted with a range of different cameras.

One particular use for a drone is in crop research, which makes use of a technology known as NDVI (Normalized Difference Vegetation Index). This is the sum of the reflectivity of near IR radiation subtracted from the reflectivity of the red light. This is then divided by the sum of the reflectivity of near IR radiation plus the reflectivity of the red light.

This formula was devised based on the basic principle that plants reflect a lot of near IR radiation, where most non-plant objects do not reflect this. When plants becomes dehydrated or stressed they reflect less near IR, but the same amount in the visible spectrum. When the two types of information are combined, it is possible to visually differentiate not only between what is plant and non-plant but also which are healthy and unhealthy plants.

Advances in drone and satellite technology benefits precision farming because drones take high quality images, while satellites capture the bigger
picture. Light aircraft pilots can combine aerial photography with data from satellite records to predict future yields based on the current level of field biomass. Aggregated images can create contour maps to track where water flows, determine variable-rate seeding, and create yield maps of areas that were more or less productive.

In the American Midwest (US), it is associated not with sustainable agriculture but with mainstream farmers who are trying to maximize profits by spending money only in areas that require fertilizer. This practice allows the farmer to vary the rate of fertilizer across the field according to the need identified by GPS guided Grid or Zone Sampling. Fertilizer that would have been spread in areas that don’t need it can be placed in areas that do, thereby optimizing its use.