UAV Systems have been a hot topic in farming for the past couple years now. UAVs are Unmanned Aerial Vehicles and they are used in a variety of Agricultural applications to do things like scout fields. Utilizing UAVs for crop scouting allows users to become more efficient and cover more ground while at the same time, capture valuable information from a different perspective than is typical with ground scouting by foot or in a vehicle.
Flight Craft Types
There are generally two types of flight craft when it comes to agricultural UAV systems. The first is the multirotor, as you've seen throughout this website, and the second is the fixed wing. Multirotors are typically used for crop scouting due to their high definition imagery, stable footage, vertical take offs and landings, the ability to stop mid-flight and take pictures, as well as a variety of other reasons. Fixed wings on the other hand are typically used for mapped imagery. Many times this imagery is multispectral, such as NIR imagery which can then be used in NDVI imagery. Fixed wings are generally used for these types of applications because of their sustained flight times (typically between a half hour to over an hour), autonomous (the ability to fly waypoints) flight features, as well as a variety of other reasons.
Flight Controller Types
There are two types of flight controllers in UAV systems. The first is the semi-autonomous flight controller. A semi-autonomous flight controller is a flight controller that provides computer assistance to the pilot as they are flying. In essence, a semi-autonomous flight controller makes it easier for a pilot to operate an aircraft as the sensors and computer on board will adjust for things like wind or sudden pitch changes for example. A fully autonomous flight controller is a controller in which the computer completely controls the aircraft. Basically a pilot sets up a waypoint route and the unit takes off itself, flies itself, takes pictures itself, and lands itself. On most of today's current UAV systems, the flight controllers can operate as semi-autonomous controllers or fully autonomous controllers depending on how the user elects to fly the aircraft.
There are three main imagery types used in Ag UAV scouting. The first is visible light spectrum imagery, or imagery that is based on what the naked eye can see, such as color differences. The second type of imagery is called Near Infrared imagery or NIR Imagery. This type of imagery picks up Near Infrared light reflectance of a crop canopy. In general terms a healthy crop will reflect Near Infrared light and absorb visible light, which it uses in photosynthesis. An unhealthy crop will do the opposite. Generally NIR imagery is combined with visible imagery and a formula is used to calculate the ratio of reflectance between the two. This formula is called the NDVI or Normalized Difference Vegetation Index Formula. The results of an NDVI analysis scores a field based on relative plant stress and color codes the field based on these scores. The picture here shows what a finalized NDVI image looks like. The final type of imagery most used in agriculture is thermal infrared imagery, a type of infrared imagery on the opposite side of the IR spectrum from NIR light. Thermal imagery is most often used for animal operations although there has been some investigation using it for agronomy as well.