Drones and UAVs: What is available now and what is possible in the future

Introduction

Unmanned Aerial Vehicles (UAV’s) or drones as they are more commonly known have increased with popularity and functions in the last few years. Originally developed by the military, the technology has become more freely available through free open source software and more affordable platforms. The UAV is allowing users to place cameras in the sky in situations that may be too hazardous or too expensive for normal aircraft such as bushfires, policing, television filming and now agriculture.

The UAV that B&W Rural have purchased is a flying wing design; powered by lipoid batteries with electric motor, wingspan of 1.4 metres, and flight time of 30-35 minutes. This allows for a maximum coverage of 150-180 hectares per flight. The area covered is reduced with decreased height; with height determining the end pixel resolution. The time taken to process the image through software is approximately 100 mins per flight to produce and image. Further processing would be required to make prescription maps however this should only be 15-20 mins, with ground truthing taking place in consultation with growers and consultants.

Flying height is restricted to 400ft AGL as per the Civil Aviation Safety Authority (CASA) restrictions and for safety to other aircraft that may be operating in the vicinity. CASA currently require commercial operators to be licenced. The use and operation of UAV’s is a grey area at the moment with regulations still being compiled. The United States safety authority, the FAA are continually making changes to both commercial and hobbyist uses with tighter regulations being introduced; I’m sure CASA is taking note and may implement some of the same regulations in Australia. B&W Rural are currently in the process of becoming licenced to provide a commercial service.

The goal of the UAV is to be able to provide another tool to growers in the decision making process that enables an issue to be identified and/or monitored, treated and followed through to yield. The ultimate goal is to enable consultants and growers to identify better management practices that achieve higher yield and profit outcomes for growers.

The UAV will be another component of precision technology that most growers are already using such as yield mapping, EM surveys, satellite NDVI imagery, and will be used in conjunction, not necessarily as a replacement. It will allow for the collect of real time data that can be related to current issues or treatments.

An example of how the UAV would be utilised:

Data collection (UAV-NDVI, satellite, EM, yield maps) >

Software analysis > crop image >

Interpreted and ground truthed >

Variable rate prescription map (computer generated and geo referenced) >

Treatment (fertiliser, fungicide, soil amelioration) >

Measured outcome (increased yield, higher protein, improved quality)

What are the current uses?

The current use of the UAV is to produce Normalised Difference Vegetation Index (NDVI) images. NDVI images have been used for decades to measure plant biomass and distinguish the differences in a specified area. It is a measure of the Near Infrared (NIR) and visible light spectrums (VIS) red, green or blue; which has the equation (NIR-VIS) / (NIR + VIS) which is applied to each pixel to give an index of values between -1 and +1.

Live green plants absorb solar radiation as a source of energy for photosynthesis. Leaf cells have also evolved to scatter solar radiation in the near-infrared spectral region as it is not useful in synthesizing organic molecules. A strong absorption at these wavelengths would only result in overheating the plant and possibly damaging the tissues (Wikipedia, NDVI). Therefore by measuring if a plant is less or more reflective in a particular wavelength, it can be used to create a map of plant health/stress and crop biomass which can be related to a particular issue in the crop.

A small modified camera can be mounted in the front and flown over a field just about anywhere on any given day to capture a series of images. The small images can be stitched together to generate a whole field image. This image is then processed through a software program to generate the NDVI image of the field. The image highlights different areas of plant biomass which can be related to the current crop by in the field reference, to any known issues or crop treatments such as fertiliser applications, disease or insect outbreaks.  

The software also allows for filtering out different types of light (wavelengths) from the data set such as the green, blue or red wavelength. This may provide capacity to identify different weed spectrums to be distinguished and digitised; however this capacity has yet to be developed.

As NDVI is essentially a measure of crop biomass and stress; it is a good tool for measuring enhanced crop growth as a result of a fertiliser, fungicide or herbicide treatment and comparing it to a nil strip. This would allow for an early comparison and then subsequent in crop decisions can be made to the current crop and applications, or for future crops particularly for micronutrients.

A list of potential uses

• Nutrient strip trial comparison
• Prescription maps for residual herbicides for hard to kill weeds
• Trial product effects
• Spray drift mapping
• Horticulture monitoring
• Targeted soil amendments such as gypsum applications
• Location monitoring of new insect outbreaks
• In crop disease monitoring

If there is a variation in plant biomass or plant health in a specific area and there is a need to quantify the extent of the issue, then the UAV should be able to help identify the issue and aid in the decision making process for the appropriate action.

Limitations of the technology are the time taken to process and store the large amount of data that is generated; however this is limited by computing power and software. Additionally to produce geo-referenced images that can be exported for in field uses takes more time and advanced technology to produce, which comes at a price.

The UAV is also still limited by battery power and area coverage, and cannot map a whole farm once a week without great effort. It is still a supplementary monitoring tool at this stage, not a problem spotter. However as the technology progresses and is improved I see it potentially becoming an everyday tool of the future for monitoring crops on a weekly basis.

Costs

UAV platforms start from $1,000 for modified toy model planes with basic non licenced software and programs written by UAV enthusiasts. This software is great for hobbyists but should not be trusted to carry out commercial works, especially in a regulated industry. From there it advances into the $15,000-$30,000 for commercially produced and warranted products.  Generally the more you are willing to spend the more advanced and versatile the technology becomes; with some platforms $80,000 plus.  

The cost of a UAV service from B&W Rural has yet to be determined. Current target markets are small areas with known problems or treatments, and preferably an untreated area for comparison. However for large scale operations greater than 5000 ha, the UAV would be best suited to supplementary imaging that would follow up on images retrieved from satellites.

The future

The use of UAV’s is extremely new to the agricultural industry and it is the horse before the cart. As the industry grows, new uses will be developed. Researchers are looking at new ways of analysing imagery, with focus on possible specific weed light signatures and instruments to measure heat signatures. It is a matter of using this technology and working with researchers and academics to develop the eye in the sky on a small scale, for use first up on a paddock by paddock and metre by metre basis.

The UAV will be another precision technology tool that will become available to farmers to utilise as different imaging techniques develop.

References

http://en.wikipedia.org/wiki/Normalized_Difference_Vegetation_Index

Contact details

Brad Donald & Peter Birch
B&W Rural, Moree
Ph: 0427103739, 0428669158      
Email: Bradley.donald@elders.com.au