Information Sheet
IS14014
GPS/GNSS for Agriculture
Global Navigation Satellite Systems (GNSS), commonly known
as Global Positioning Systems (GPS) involve a variety of
components and are most commonly used in agriculture for
navigation.
GPS is the term for the US NAVSTAR satellite system. Other
systems are being developed by other countries such as
Russia’s GLONASS and the EU’s Galileo.
In a GNSS, satellites orbit the earth and send signals to
receivers that can give highly accurate information about their
location on the earth’s surface.
Currently the US’s NAVSTAR GPS and GLONASS are the only
satellite systems that are fully operational. Availability of
multiple satellite systems can help improve the availability of
signals, but only if the equipment you purchase has the ability
to receive signals from each system.
Different levels of positioning accuracy are available depending
on what you are trying to accomplish. As you would expect,
higher accuracy comes with a higher price tag. Table 1 gives an
overview of some of the options.
Right (top image): This shows a GPS receiver and antennae
that receive differential signals.
Right (bottom image): This shows a tractor operator using the
in-cab display to use GPS guidance in the field.
Table 1: GPS options.
Type of GPS
Accuracy
Average Cost
Agricultural Uses
Stand-alone receiver: usually
a handheld unit that receives
satellite signals
~4–10 m
AU$100-1000
• Recording location of on-farm activities such as soil and tissue tests
Differential receiver: receiver
plus additional fixed, groundbased reference stations to
correct errors in original signal.
May require a subscription.
~0.1–1 m
Real-Time Kinematic (RTK)
differential receivers: type
of differential receiver where
correction signal comes from a
local base station in real-time.
2–10 cm
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• Strategic trials
Up to
AU$10 000
Everything above plus:
• Guidance
• Yield Mapping
• Variable-Rate Control
AU$10 000
–40 000
Everything above plus:
• Autosteer
• Elevation mapping
• Land levelling and forming
Information Sheet
IS14014
The most common type of GPS used in precision agriculture
is RTK. The accuracy of different RTK systems varies slightly so
make sure you understand the terminology dealers are using
before you make a decision about what to purchase.
Benefits of satellite navigation
Most of the benefits of satellite navigation result in improved
efficiency of farming operations that help farmers save time
and money. Some of these benefits are listed below.
• reduced skip and overlap of inputs
• reduced driver fatigue
• reduced compaction
• improved soil water management
• increased yield
• inter-row cultivation, spraying, and planting.
Agricultural uses of GPS
(http://www2.ca.uky.edu/agc/pubs/pa/pa5/pa5.htm)
Above: A differential GPS system uses a ground-based
reference station to increase the accuracy of the location
information. RTK receivers get their correction signal from a
local base station in real-time.
Satellite navigation definitions
Sometimes these terms are used interchangeably, but they
actually mean different things.
• G
uidance: GPS guides machinery but control remains with
the operator. The guidance system uses a signalling device
to prompt the driver to maintain a predetermined path.
Requires sub-metre accuracy of GPS signal.
As listed in Table 1, there are a variety of agricultural uses
of GPS besides navigation. A common thread amongst
all of these activities is the use of spatial data. When you
have access to specific information about where different
things are happening on the farm, this can help you better
understand your land and give you more confidence in making
management decisions.
In addition to the spatial information provided by GPS,
agricultural GPS equipment and accompanying software
can be used for automated record keeping and inter-vehicle
communications, among other things. Understanding your
equipment and all of its capabilities can help you streamline
your farming operation to become more efficient and
productive.
References
Whelan, B. and J. Taylor. 2013. Precision Agriculture for Grain
Production Systems. CSIRO Publishing. 199pp.
• A
utosteer: Removes operator from the majority of steering
operations. For safety, autosteer systems have an automatic
override system as soon as the operator takes control of
the steering wheel. These systems also monitor the quality
of the satellite signal. Requires centimetre accuracy of GPS
signal.
• C
ontrolled Traffic: The use of guidance or autosteer to
confine all machinery loads to the least possible area of
permanent traffic lanes.
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