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Technology

Drones: Benefits, restrictions and uses

By Hantie Jansen van Vuuren
Nutriology Solution Marketing

If you are old enough to remember the science fiction stories of the seventies and eighties, you might recall pictures of self-driving cars and robots that serve humans. Those pictures were often captioned: “In the year 2000 …”. Throughout the ages, even as far back as the 1800’s, people have dreamed about the technological age that we find ourselves in today.

Figure 1 – 2: Depictions of the year 2000
Figure 1 – 2: Depictions of the year 2000

The arrival of the year 2000 was a bit disappointing in terms of technological advancement. Yes, we were introduced to cellular phones, television sets became flatter and the appearance of motor vehicles changed, but the majority of things pretty much remained the same.

However, things have started to change rapidly in the last few years. Many works of science fiction involve technological speculation that bears remarkable resemblance to the technology that we use today. 

Not only are there advances in the use of robotics and autonomous vehicles, but remarkable developments are happening even in agriculture. This leads to the question: Which of these modern technologies are really worth the effort? And how does it work?

With so many new advances in agriculture, we will be focusing only on the use of drones in this article.

What are drones?

Drones, also known as Remotely Piloted Aircraft Systems (RPAS) in South Africa or Unmanned Aerial Vehicles (UAVs) in the USA have been around since the early 1980’s, but their application in agriculture is a popular topic today. Trials are being conducted with drones performing electromechanic soil surface measurements, planting drones that shoot pods with seeds and plant nutrients into the soil and drones being used for extra fast spraying of chemicals. In China, they even used a drone to apply liquid fertilizer (https://www.youtube.com/watch?v=P2YPG8PO9JU).

Some visionaries foresee a future where fleets or swarms of autonomous drones tackle agricultural tasks collectively and hybrid aerial-ground drones collect data and perform a variety of other tasks1.

With all the challenges facing farmers today such as climate change, unfavourable price ratios and the ever growing need for agricultural land, the need to farm more economically and ecologically sustainable is now greater than ever. If drones can help to reduce risk and increase yield, it has to be seriously considered. But how do we know if this is a good investment?

Drones as part of precision farming

According to Tom McKinnon from Agribotix, drones can be used to contribute to the data layers that drive precision nutrient and irrigation management2. Other sources of data for these layers are yield monitors, soil sample results, moisture and nutrient sensors and weather feeds. In addition to these historical data sets, new technologies such as satellites and drones, can provide a view of the current condition of the in-field crop.

Whole-field, in-season, current condition data is one of the most valuable pieces of information in a precision programme. This data enables a farmer to detect problems early on and to select appropriate interventions. Spot-checking, the most common method used to get this information, does not accurately capture conditions across an entire field. This is especially true for very large fields.

Manned surveillance flights and satellites using near infrared cameras, also called NDVI (Normalised Difference Vegetation Index) cameras, and RGB (Red, Green, Blue) cameras used to be the incumbent data sources for whole field condition assessment, but these were only suited for surveying thousands of hectares at a time, where the time and resources required justifies the expense and complexity. However, due to the flexibility and relatively low cost of drones, these other remote sensing methods have become more affordable. Each method has its own advantages and disadvantages, however new advances in satellite and drone technology is busy eliminating some of the disadvantages.

Agricultural drones represent a new way to collect field-level data. The most compelling reason for using drones is that the results are on-demand. A drone can easily and quickly be deployed whenever and wherever needed. It’s hard to beat the immediacy and convenience of planning the mission, collecting the data and getting near real-time results – only drones offer these benefits.

Regulatory aspects of flying a drone

In South Africa, hobby drone pilots do not need a licence, even though they have to adhere to certain flight regulations. However, these pilots are only allowed to use drones for recreational purposes, in other words, for fun. Once a drone is used in a business such as a farm, even if the use of the drone is not charged for, the business owner has to apply for a corporate RPAS operator’s certificate (ROC) from the South African Civil Aviation Authority3.

The Omnia Group has applied for a corporate operator’s certificate a few years ago and has only now reached phase four of the certification process. There are five phases in total. This is not an easy process and should only be considered by companies or persons who are totally committed to drone flights as a service. For this reason, it might make more sense for a farmer to employ the services of a reliable contractor to handle this side of the business.

Drones best suited to agriculture

While there are many drones available today, not all of them can be utilized in agriculture. Those that are suitable for farming, fall into two categories: fixed-wing and multi-rotor drones. The cost and payload capacity of both types are similar.

Fixed-wing drones
Multi-rotor drones

These have long-range flight capacity – an advantage with large areas. They are also crash tolerant. Because these drones can cover great distances, they can be challenging to keep in the operator’s range of sight, which is a legal requirement.
Image quality can suffer as a result of their greater speed. For example, fixed wing drones are often unable to capture survey-grade 3D / topographic detail.

Faster to set up in the field, these can take off and land vertically. The mission set-up is simple; there is no need to plan take-offs and landings into the wind as with the fixed-wing type. For inexperienced operators, these drones are the easiest way to get it up and running quickly. They have the ability to fly more precisely, as they can turn sharply where fields are next to roads. They can also fly at low altitudes if extremely detailed images need to be captured.

With either type of drone, the actual flight process is relatively straight forward. Using software on a device (typically a tablet, laptop or smart phone), the operator draws an outline of the area to be surveyed on a Google map type of view. The software programmes the flight, overlaying lines on the map to show the drone’s flight path. The information is uploaded to the drone via a wireless link. With some drones, take-off, flight and landing are completely autonomous, although a manual override allows the operator to avoid unexpected objects in the flight path. However, many operators prefer to fly their drones manually.

Except for the expensive and cumbersome licencing and registration procedures, some of the other limitations of drones that have to be kept in mind are the battery life, the size of the field and the wind. Strong winds have a substantial influence on the planned flight path and the frustration levels of the operator.

Drones have a variety of different sensors and cameras available. NDVI is a vegetation index that is useful for a variety of agricultural purposes. An NDVI can clearly distinguish areas of the field where a crop is growing well from those where it is not. Due to the way the plant reacts to stress, an NDVI image can also reveal the presence of weeds, pests, water damage and other problems. A variety of other vegetation indices also exist (https://en.wikipedia.org/wiki/Vegetation_Index).

Other types of drone-mounted sensors for agriculture reports; plant counts, plant height, field uniformity, soil water levels, soil temperature and topography/3D mapping.

Data analysis

Obtaining understandable, actionable data in a timely fashion is essential. Software that can handle a large volume of images quickly and return analytics that both identify issues and make recommendations for intervention and variable rate application can mean lower input costs, a larger yield and increased profit. Look for options that provide a range of specialised agricultural intelligence and produce outputs in formats compatible with precision equipment. The key is to choose a software platform that is easy to use and won’t require the user to monitor processing.

Recommendations

According to Tiaan Terblanche, Business Development Manager at Axioteq, drones are much more useful and relevant in high value or permanent crops where the orchard or field is relatively small and where high resolution images are necessary.
“I am talking about 15 cm resolution images, which are essential for these types of crops, but will be over-kill in grain crops and sugarcane. For grain crops, satellite images are a better fit, because the fields are much larger. A drone will struggle to complete a farm of 750 hectares in one week,” says Terblanche.

It is important to note that drones and manned flights will provide a once-off image, but that satellites monitor the field continually, as satellite images are sold as a seasonal subscription.

To summarise, it is recommended that manned flights (fixed wing) and drones be used in high value crops (vegetables) and permanent crops (trees and vineyards). For larger areas, only manned flights should be used. The Omnia Group employs contractors to manage both manned and unmanned flights. For grains and sugarcane, 10 m and 5 m resolution satellite images are recommended throughout the growing season.

Agricultural drones are here to stay. It can be of great benefit in farming operations, however, as with all new technology, proper research into all of its aspects is necessary to decide whether, and where, drones should be employed in your farming business.

Primary references:
  1. Mazur, M. (2016) Six ways drones are revolutionizing agriculture. MIT Technology Review. https://www.technologyreview.com/s/601935/six-ways-drones-are-revolutionizing-agriculture/
  2. McKinnon, T. (2016) Agricultural drones: What farmers need to know. Agribotix white papers: https://agribotix.com/whitepapers/farmers-need-know-agricultural-drones/
  3. South African Civil Aviation Authority website:
    http://www.caa.co.za/Pages/RPAS/Remotely%20Piloted%20Aircraft%20Systems.aspx