Precision Viticulture
Unmanned Aerial Vehicles
Advances in technology have made the use and availability of unmanned aerial vehicles (UAVs) "better known as drones" an increasingly more frequent occurrence in the vineyard. With the rise of UAVs growers are exploring options for employing these machines in their daily operations. Without question UAVs can provide a multitude of opportunities for wine grape growers. They can fly up to an altitude of 400 feet (122 m) and are able to follow the same path or GPS-guided routes daily, weekly, or as desired. The increased availability of these relatively cheap and simple-to-use UAVs makes drones perfect for growers wanting more detailed information on the vineyard in a timely manner.
Advantages and Disadvantages
There are three main advantages in using a Unmanned Aerial Systems (UAS) for disease and stress detection. The first advantage is cost. Collecting images and data are less costly by UAS than by satellite or manned airplane. The second advantage is timeliness. UAS have the ability to fly and capture images on short notice or during small windows of opportunity.
In spite of the potential advantages of UAVs in agriculture, there are several challenges that must be addressed before these machines truly can be used for disease and pest scouting. The first challenge is the lack of suitable, lightweight and cost-effective sensors. The common multi-band cameras that are commercially available have limitations, either in optical or spectral resolution.
Types of Drones
Many types of drones are available today, but not all are good candidates. Those suitable for agricultural applications fall into two categories: fixed-wing and multi-rotor drones. With either type of drone, the actual flight process is relatively straightforward. Using software on a ground control device (typically, a tablet, laptop or smartphone), the operator draws an outline of the area to be surveyed on a Google map type of view.
Fixed Wing
Fixed-wing drones are designed like more traditional types of aircraft—which look like an airplane (See Figure 34.4). They are made of a central body that has two wings and a single propeller. Once in the air, the two wings generate lift that compensates for its weight—allowing the aircraft to remain in flight. While this type of aircraft is less common in drone mapping outside of the agriculture, oil, and gas industries, they present some advantages. Fixed-wing drones have long-range flight capacity, an advantage when a large area is to be covered. Because fixed-wing drones can cover great distances, they can be challenging to keep in the operator’s range of sight, a requirement under current Federal Aviation Administration (FAA) rules.
Multi-Rotor
Multi-rotor drones are faster to set up in the field and can take off and land vertically (See Figure 34.5). They are made of a central body and multiple rotors that power propellers to take flight and maneuver the aircraft. These usually have four rotors (quadcopter), but can have as many six or eight (hexacopter and octocopter). Once in the air, multi-rotor drones use fixed-pitch propeller blades to control the vehicle motion by varying the relative speed of each rotor to change the thrust and torque produced, allowing a unique range of movement.
Sensors
Today, a wide range of optical imaging systems are available which can be integrated with unmanned aerial systems (UAS). In general, optical sensors are classified based on the form of data acquired and source of electromagnetic radiation (EM) used to measure the response. A range of active and passive sensors can be integrated with small UAS.
RGB Sensors
RGB sensors are the least expensive of all the cameras but also provide the least amount of information and uses. They only capture visible light (red, green, and blue).
Multispectral Sensors
The multispectral sensor is one of the most commonly used scanning systems. Multispectral sensors allow specific ranges of the electromagnetic spectrum to be captured. They normally capture 4 to 7 bands.
Hyperspectral Sensors
Hyperspectral sensors collects and processes lots of information from the electromagnetic spectrum. Its goal is to obtain the spectrum for each pixel in the image to find objects and identifying materials.
LiDAR Sensors
LiDAR is a more traditional surveying tool used for creating point clouds and digital elevation models of the ground. The data can be used for plant height measurement by comparing the first return from the laser when it hits the top of the plant to the last return when it hits the ground.
Web-Based Service Providers
When a drone collects data over a vineyard, the camera takes several hundred still images as it flies a “lawnmower” pattern back and forth across the field. These images then performed to make the results useful. A computer with specialized software can process the images locally, which can be time consuming on several levels. Gaining mastery of the software initially and achieving repeatable results, flight after flight, can be a steep learning curve. The processing itself can tie up the computer for hours each time new data is loaded, suppressing productivity and requiring the operator to be present to monitor progress. Alternatively, processing can be done using a purpose-built, web-based service. In this model, the operator performs the flight, runs software that automates image collection, and uploads to the cloud.
Regulation by Federal Aviation Administration
Federal Aviation Administration (FAA) regulates use of all UAVs. The FAA announced in February of 2015 the long-awaited Notice of Proposed Rulemaking for UAVs. Under the new FAA proposal, drones that weigh less than 55 pounds would be able to fly up to 500 feet above the ground at speeds up to 100 mph.
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