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.

What will you use it for?

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

© Gary Naylor

Any drone is a means of transporting a camera or other sensor capable of surveying crops remotely. A summary of the main camera types and their potential uses is shown below.

See also: 2 arable farmers explain how they use drones

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.

Sensor types

Camera type

What’s it for?

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

Mr Wrangham also advises farmers to be wary of cheap “multi-spectral” cameras that use a single modified lens to detect different light wavelengths.

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.”

Cost

While it is possible to buy a recreational drone for sub-£50, farmers may need to spend £300-400 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 thousand pounds. This in turn means you will need a more robust, reliable and accurate drone.

What type?

Drones can be divided into three 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, 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 four motors (quadcopters), six motors (hexacopters) or eight (octocopters) motors.

Mr Eglington says those with six or eight motors can usually keep flying when one or even two 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.

Specification and features

Drone equipment – cameras, motors, gimbals, sensors and microprocessors – is developing rapidly and costs keep falling.

Feature that were once only on top-end drones are increasingly offered with more affordable models, while the capabilities of premium models are increasing.

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.
  • Know the rules – caa.co.uk/drones.

See also: How to stay legal when flying drones over arable crops

Software

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 (£80-$240) per month. Other advanced software can cost several thousand pounds.

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.

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.

Cereals show

© Tim Scrivener

See drones in action

See how drones can benefit your farm and business in the Drone Zone at Cereals 2017, Boothby Graffoe, Lincolnshire, on 14 and 15 June.

The area is dedicated to showcasing drone flying, image capture and data analysis and has been expanded for 2017 to comprise:

  • Flying cage for short flights and presentations
  • Field, complete with crop, for longer flights
  • Big screen to display data

Find out more at www.cerealsevent.co.uk/drone-zone