Drones are widely recognised as a useful tool in arable farming. But how to buy the right drone for the job? Here’s a grower’s guide to buying a drone.
Unmanned aerial vehicles (UAVs) – or drones – have come a long way since the first commercial use in Japan during the 1980s, with a plethora of systems and potential applications now available to suit all budgets.
Several hundred manufacturers supply equipment to this fast-moving global market, where drones can cost anything from £50 to tens of thousands.
There are plenty of potential uses for drones in agriculture, so before buying anything it is essential to be clear what it is needed for, as this determines the type – and likely cost – of the system required.
Drone and camera sold together
Any drone is a means of transporting a camera or other sensor capable of surveying crops remotely. While it is possible to buy the drone and camera separately, many are sold together. Jack Wrangham from mapping and spraying firm Drone AG believes buying a ready-to-go integrated system can save a lot of hassle, even if it is slightly more expensive.
There may be compatibility issues when buying equipment separately, and some drones do not allow the camera to be changed, he says.
Mr Wrangham also advises farmers to be wary of cheap “multi-spectral” cameras that use a single modified lens to detect different light wavelengths.
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Any drone is a means of transporting a camera or other sensor capable of surveying crops remotely. - Photo: Anne van der Woude
A true multi-spectral camera has separate sensors and lenses for every spectrum of light measured, to give much more accurate results.
“The difference can be £300 versus £3,000, but a single modified lens may not give much more detail than a standard RGB camera.”
Camera types and how they can be used
- High-resolution visible RGB (red, green, blue) (minimum 12 megapixels): High-resolution colour pictures (RAW/JPEG format) for visual inspection, basic elevation mapping, plant counts
- Thermal infrared: Crop physiology/maturity analysis, yield forecasting, irrigation scheduling
- NIR (near infra-red): NIR photos for crop health vegetation indexing (NDVI maps), soil property and moisture analysis, plant counts
- RE (red-edge): Crop health analysis, plant counts, water management
- Lidar: Detailed 3D mapping
While it is possible to buy a recreational drone for around 60 dollars, farmers may need to spend 400-500 dollars or more for a reliable system with an RGB camera capable of good aerial imaging and video recording. Such imagery can highlight field problems associated with poor drainage, weed infestations or pest damage.
More complex crop imaging – such as measuring green leaf area, disease or weed identification – requires more sophisticated (and expensive) multi-spectral or thermal imaging cameras, typically costing several thousands of dollars. This in turn means you will need a more robust, reliable and accurate drone.
What type of drone?
Drones can be divided into 3 main categories based on their drive mechanisms: multirotor (multicopter), fixed wing and hybrids (wings and motors). Multicopters are the most common, accounting for about 95% of the UK agricultural drone market alone, according to Chris Eglington, Norfolk farmer and co-founder of UAV spraying company Crop Angel. Cheap multicopter models are easy to fly and can be operated solo, whereas fixed-wing drones fly faster and longer, but often require help to launch and spotters on the ground to maintain visual contact, he says. Multicopters typically have either 4 motors (quadcopters), 6 motors (hexacopters) or 8 (octocopters) motors.
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Drones can be divided into 3 main categories based on their drive mechanisms: multirotor (multicopter), fixed wing and hybrids (wings and motors). - Photo: Ronald Hissink
Software prevents crashing
Mr Eglington says those with 6 or 8 motors can usually keep flying when 1 or even 2 motors fail, but tend to be bigger, heavier and more expensive. Many quadcopters fall to ground when a motor fails. However, some new models include software that puts the drone into a spin, giving the pilot more chance to land it, he says.
Key features to consider when buying include:
- Motors: how many and what is the average lifetime (flying hours)? Motor failure is the most common fault, although brushless motors on commercial drones are more powerful and reliable than cheaper versions.
- Batteries: typically last 300-400 charge cycles and cost about £150 to replace. It is worthwhile having a spare. Check charge time duration.
- Safety features: GPS auto-hover and auto-fly home when battery is low or signal is lost are on most drones. Check how many GPS sensors are fitted and what happens if a sensor fails.
- Weather resistance – most drones cannot be operated in rain or winds above 10-15mph, but some are more “weather-proof” than others – GPS-enabled drones are better at maintaining position when hovering in light winds.
- Consider the warranty available, the level of technical support and the availability of spares if needed.
- Try before you buy – not possible if buying online.
The cost of the computer software needed to analyse data collected by any drone must be considered before buying. Prices vary considerably depending on the data being processed and whether you buy a package outright or opt for a monthly subscription. For example, a free version of the popular DroneDeploy software can be used for stitching together images to generate colour maps. Advanced packages for 3D mapping or vegetation indexes cost $ 100-$ 300 per month. Other advanced software can cost several thousands of dollars.
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Yamaha Motor has moved into markets beyond Japan with its remote-control spraying and spreading helicopters. The 32 litre (8 gal) capacity Fazer R has ‘turn assistance’ to automatically maintain correct pass spacing. - Photo: Yamaha
Multicopters typically have either 4 motors (quadcopters), 6 motors (hexacopters) or 8 (octocopters) motors. - Photo: DJI
Also consider what support is available and what internet connection is required, especially if large data files need to be transferred to cloud-based systems, says Mr Wrangham. In particular, check your upload speed and any data allowances for uploads set by your internet provider. Many contracts offering unlimited downloads still cap uploads, and exceeding these limits can be expensive, he warns.
Specialist company for analysis
Buying software outright may be one solution, although advanced packages can require significant processing power, which may be beyond some farm computers. Another option is to send data to a specialist company for analysis. This saves paying for software, but again requires a good internet connection because of the large files involved, says Mr Eglington.