/20th September 2017, Alfonso Torres-Rua/ Multiple drones or UAV devices are available in the market for agricultural purposes, and some of them are already being used in Utah farmland. Because drones are available, it is important to determine their capabilities. The camera sensors are key to the quality of maps produced by the drones. In general, low cost sensors that capture red-green-blue (RGB) and near-infrared (NIR) pictures are not necessarily calibrated for agricultural purposes.
These cameras are intended for human portraits and nature photography and video, thus they are calibrated to capture light that describes these scenes. These types of sensors are found in Go-Pro, Canon, Sony, and any other camera brand found in a photography shop. Agricultural type cameras have specialized filters that make them more expensive. Examples of specialized cameras for agriculture are the Micasense Red-Edge, and Parrot Sequoia. These cameras are lightweight and specifically designed for UAV power support.
Another major key in UAV use is the location accuracy on the ground of the pixels captured by the camera mounted in the drone. Like available agricultural equipment, UAVs have incorporated GPS which records the location of the UAV while in flight. Nevertheless, the accuracy of the GPS device can be +/-10 ft, which means the device could locate the UAV images out in the road or in next field. If the results of the UAV are for more than simple visual inspection, investing in GPS ground targets, such as the ones provided by Propeller, or ground mats can provide a solution to the problem.
One of the map products that can be obtained using commercial UAVs is the Normalized Difference Vegetation Index (NDVI) or similar. The NDVI is an index that indicates the overall health of a plant. If the NDVI values are close to 1.0, vegetation is expected to be healthy, but for values close to 0.0, the map is showing bare soil or stressed vegetation. Different cameras will give different values of NDVI for the same field and flight time, which could mislead the user of the UAV NDVI map. Agricultural cameras, however, can provide a standard NDVI that is comparable with other agricultural cameras such as those in satellites.
UAVs tends to be time and money intensive because of the multiple conditions required for its use: FAA regulations, UAV flight by a licensed pilot, and processing capabilities to obtain the RGB or NDVI map. FAA regulations limit UAV flight s to an elevation of 400 ft. and to ~1.8 miles (visual line of sight). The FAA also requires all UAV flights that benefit commercial applications (e.g. agriculture) to use a licensed UAV pilot. UAV flight data must be transferred into a cloud solution or a local powerful computer for processing. Cloud solutions tend to require an annual fee, and computer solutions often require a fee or a license.
The full research paper you can download from here: Drones in Agriculture: An Overview of Current Capabilities and Future Directions