How to pick the right drone for your farm

When one mentions farm equipment, tractors and balers spring to mind but one unassuming newcomer is taking the agricultural industry by storm.

Enter the drone or unmanned aerial vehicle (UAV), which started out as more of a recreational or cinematography gadget, but has evolved over time to include a smorgasbord of technology and sensors capable of collecting farm specific data such as soil moisture and plant height to help farmers manage their crops, farm and livestock better.

Drones for ag use can be widely categorised into two types: fixed wing and multi-rotor.

Which one to go for depends on a number of factors including what you need them for, what conditions you will be flying in, your budget and more.

One thing to keep in mind is that UAVs for professional or industrial use come with bells and whistles that recreational or consumer drones don't, which means they cost significantly more. Therefore, it’s wise to do your research to decide which one suits and if you really need one.

Here, we break them down…

Fixed wing drones are units with wings on either side of the aircraft, much like a commercial airplane, and will need to be launched via a runway.

Priced from $5000, fixed wing aircraft for ag-use weigh from two to 5kg and are made from high-density foam and carbon fibre, giving superior flight and landing attributes, and includes a multi-spectral sensor for crop NVDI analyses.

However, in windy conditions, the lighter weight aircraft can be buffeted around.

They can fly up to 120m above the ground, taking crop pictures of 15cm pixels, covering over 80ha an hour.

“They have an air speed sensor, a barometer and a GPS for processing on the fly, sending their data via radio transmission back to a ground station, including devices such as iPads, notepads, laptops and phones, and allows fully autonomous flight,” said Lachlan Feeney from drone services company, Australian UAV.

Then we move into the tall end of the fixed wing world with large wing span UAVs, possibly with two engines, and the hectares which can be assessed grow exponentially.

Feeney uses a fixed wing UAV for forestry work, flying for up to two hours to capture pine plantation health or counting juvenile trees and their success, for example.

“Both fixed wing and multi-rotor drones carry cameras but fixed wings have an added complexity of not being able to hover,” Feeney said.

“Multi-rotors are stable, can hover and are simple to use but the trade-off is area captured.”

Multi-rotors with additional sensor weight have about 15 minutes flight time compared to an hour for the fixed wing models.

Longer flight time, can carry large payloads, captures a larger area

Can’t hover, pricier, harder to operate

Parrot Disco - Price: $6875.00

“Parrot Disco released the Pro Ag version carrying a multi-spectral camera about three years ago, and is a personal workhorse of mine because of its value for money and data quality it returns,” Feeney said.

senseFly eBee - Price: Upwards of $15,000

senseFly eBee have been doing the same thing – senseFly comes with software to process the imagery, NDVI (normalised difference vegetation index) for crops and fly the aircraft whereas Parrot Disco requires other software to extract the vegetation indices.

These are drones with more than two rotors - either four (quadcopter), six (hexacopter) or eight (octocopter). Unlike fixed wing aircrafts, these can fly vertically and hover.

A prominent example of a multicopter drone is the DJI Phantom 4, which often springs to mind when drones are mentioned. And there is certainly a lot of them getting around.

“When people think ag drones, they think of big hexacopters but some of the consumer grade off-the-shelf Phantom drones can achieve an ag result,” Feeney said.

“They have a fantastic 4K camera for a retail drone so you get a lot of bang for your buck.”

“Processing data derived from the Phantom 4, for example, produces topography surface models quite well with a standard camera but seek specialist help to incorporate ground trothing if you need data which is accurate down to centimetres, for instance planning irrigation design.

“When evaluating plant health, we are looking away from red, green and blue light and into the near infrared spectrum, and up to the thermal spectrums or middle infra reds using multi-spectral sensors and thermal cameras.

“We can obtain spatial data, covert it to a script file and load into a tractor’s GPS data base for planning harvest, spraying or pesticide runs.

“These sensors start at a price point of $5000 and upwards – that is what turns the drone from a recreational or cinematography device or a racing drone into an actual piece of farm equipment.”

For drone-mounted cameras, wide-angle lenses distort images for data collection so stick with the factory mounted lens.

The camera on the Phantom provides sharp, clear data of less than 2cm pixels at 60m above the ground, enabling even leaf-by-leaf inferences.

Easy to use, more compact, cheaper

Less stable in windy conditions, shorter flight time, carry less payload

DJI Phantom 4 RTK - Price: About $6500

DJI released the Matrice 200 in Australia about two years ago as an industrial drone that is equipped with a myriad of sensors for professional applications including land surveying, search-and-rescue missions, agriculture, bridge inspections and more.

Ongoing costs of technical repairs, replacement parts, software upgrades and additional equipment can be up to 50 per cent of the purchase cost for commercial operators.

“Batteries have a limited life span and if a battery is drained too low too often, it can catch fire in the air – the most likely time for a fire will be recharging the battery or in landing when there is low voltage, and the aircraft is trying to draw a lot of amps,” Feeney said.

“Batteries should be kept in a non-combustible storage container so vehicles or sheds are not lost in the incidence of a battery fire.

“Understand what components will wear out and be prepared to fix that before it does, namely bearings, motors and batteries.

“If the motor starts to get graunchy on a drone, dust may have got into the bearings and that may cause a catastrophic failure.”