By John Stuart
In this article we discuss the use of remotely piloted aircraft systems (RPAS)
or just ‘drones’ in agriculture. This new technology has a vast range of commercial applications, and many of them are in agriculture. We give an overview
of the technology and its potential benefit to agriculture.
D
rones have become
very popular over the
past few years, sometimes controversially.
Concerns over privacy and airspace
safety have led many regulators,
including the SA Civil Aviation Authority, to introduce draconian
regulations for the commercial operation of drones, but this has still
not curtailed the growth of the
industry, or the proliferation of the
applications of the technology. In
agriculture they have been used for
crop scouting, vegetation stress
monitoring, livestock monitoring,
drainage planning, security and
surveillance, crop-spraying, bird
abatement and sample-taking.
Possibly the highest return-toinvestment for any agricultural
drone application is that of vegetation stress monitoring. This technology uses near infrared (NIR)
sensors mounted on the drone to
generate a high resolution photo
map of the fields that are scanned.
The resulting imagery is used to
create a normalised difference vegetation index (NDVI) photomap of
the fields, which are like an ‘x-ray’
of the field, showing farmers and
agronomists exactly where the
problem areas are. To the naked
eye, the fields may look uniform
and healthy, but the NDVI reveals
‘invisible’ variation in the health of
the plants across the area of the
field. The diagrams are georeferenced, meaning that problem
areas can be identified to within
2m accuracy.
Figure 1: An agricultural drone
Vegetation Stress
What, though, do the diagrams
mean by indicating ‘problem areas’? The areas that are indicated
as having a low index are indicated
in a different colour than the
healthy areas. The imagery tells us
that these areas are either stressed,
or have a low leaf area index (LAI),
or combination of both. The LAI is