As the machinery
giants throw their weight behind
GPS precision farming equipment, ultra-accurate electronic
guidance will increasingly be the name of the game. David Cousins
and Emily Padfield look at a fast-moving field
Everyone in the 1950s thought that the future would
involve a compliant robot in every home, a prediction that is still
a long way from reality. But out in the fields, technology is
arriving that makes the average car satnav look pretty primitive
and will transform the way that crops are grown.
John Deere
has already carved itself a chunk of the market with its autosteer
and is pioneering totally hands-free (including the headlands)
GPS fieldwork systems. New Holland announced at
LAMMA that it had struck
a marketing agreement with GPS equipment giant
Trimble to fit its GPS
equipment on its tractors and combines.
And just last week
Agco, which makes Massey
Ferguson, Valtra, Fendt and Challenger tractors, said that it has
entered a marketing agreement with another GPS giant,
Topcon, to sell its
equipment. Meanwhile Swiss giant
Leica has made a big push into
the agricultural guidance sector, as has US RTK pioneer
AutoFarm.
The fact that some of the biggest machinery makers
are putting their weight behind GPS precison technology confirms
what many already suspected, that this is a technology that is here
to stay. It may be bigger farmers who use it now, but the benefits
in better steering accuracy, fewer overlaps and less driver fatigue
mean its influence will no doubt spread far and wide.
And new technologies are coming along, like network
RTK that give accuracies of 1-2cm without needing a base station.
It's not cheap (and you need a decent GPRS signal) but it allows
growers to try ultra-precise RTK with a relatively low investment
in equipment.
In this feature we look at what network RTK offers
in relation to its base-station equivalent and talk to two farmers
who have tried both systems.
 |
|---|
| Joe Vaughan (left) and Jim Beeden (right) are trying
two different approaches to RTK. |
CASE STUDY – Joe Vaughan and Jim Beeden, Welton, Lincolnshire
Farming near Welton, Lincolnshire, neighbours Joe
Vaughan of RH Ward Welton and Jim Beeden of Flagleaf Farming have
both been using
Leica's Mojo RTK
system, albeit in different guises.
They'd looked at several systems and, together with
a group of farmers in the area also keen to adopt GPS technology,
even considered installing an aerial at a central point.
But they discovered this would require signal
repeaters every 20 miles or so. Even with these, signal quality
would depend on topography and vegetation, meaning some would be
left with decidedly patchy coverage.
"The cost of putting up the aerial was also
prohibitive," says Mr Vaughan. "And with developments moving so
fast, that sort of investment needs to wait until things have
settled down somewhat."
Every farmer has different priorities, so it would
have been difficult to get a system that met everyone's
requirements, Mr Beeden added.
So, both farmers started looking at the
alternatives. Both had seen the Leica Mojo RTK system at its launch
at Cereals 2008 last year and Mr Beeden arranged a unit on demo on
his Challenger.
The system itself is a straightforward plug-in item
on newer machines, but with the
QuadTrac 450
being slightly older, they had to fit a separate wiring system and
EasiSteer autosteer. Next-door's Challenger was easier as it was
already configured to "plug-n-play".
Leica's system, which comes with central console,
antennas for attaching to the top of the tractor and base station,
supports existing factory and third-party steering systems, and
claims repeatable 5cm accuracy 99% of the time.
The console fits snugly into the standard radio
slot in the cab, and comes with CD, radio and MP3
compatibility.
 |
|---|
| Chris Harwood drives the
QuadTrac. |
Once the base station is set up, it calibrates
itself by finding the satellites, which usually takes about a
minute. Generally, it needs 8-10 satellites to work at full
accuracy and if it can't find enough, it starts again, adds Mr
Vaughan.
"Having seen how simple it was, we ordered it and
had one in time for the start of cultivations in August," says Mr
Vaughan. The farm currently has a QuadTrac 535 on order, and again
the system will just plug in.
The biggest cost-saving comes from not overlapping,
he reckons. "It may not seem a lot land-by-land, but multiply this
across the field and you could be doing upwards of 20% of the field
twice."
Although Mr Vaughan uses RTK at the moment for
cultivations and drilling, he's keen to filter it down for potato
seed-bed preparation, too.
The main reason for choosing the Mojo was the cost
and simplicity of the system, he maintains. "It worked out the
cheapest that we had looked at, coming in at about £10,000, and it
does exactly what we need it to."
"It's not just the first pass that benefits from
cost savings," he adds. "Every pass thereafter, each spray
application, also has straight lines to follow."
Meanwhile neighbour Jim Beeden, a manager for
Flagleaf Farming, has been testing Leica's first network RTK
system. On the tractor you might not notice much difference in the
equipment fitted.
However the control unit has a SIM card reader in
the back which acts as a GPRS modem. It's currently fitted with a
Vodafone SIM card, which receives correction data from the Ordnance
Survey network of 90-odd masts.
This signal does the same job as the base station,
establishing the position of the OS masts in relation to the mobile
unit and comparing that to the satellite signals.
The annual fee for this service hasn't been
established yet, and it will depend on how many units use the
technology, says Mr Beeden
However in terms of overlapping alone, Mr Beeden
reckons this costs him around £8500 a year across 1400ha (3500
acres) of which a large portion is saved. So it should soon pay for
itself. "There's no doubt it's better for driver fatigue," he adds.
"And because the operator is concentrating on getting the most out
of the machine, there's definitely increased output."
He reckons it works just as well as the base
station system, and without the hassle of having to set the
receiver up in the field. His next step, he says, is to fit it to
his new John Deere 5430i sprayer and drill tractor.
RTK and network RTK – a quick
guide
How does GPS work?
GPS is based on a series of
satellites and some frighteningly accurate clocks that between them
can work out the exact position of any point on the earth's
surface. The US military has had a system for some time, but only
made the information from its 24 satellites fully available to
other users in 1993. The Russians have their own set of 19 Glonass
satellites and the EU will have its Galileo system up and running
in 2018.
How accurate is all this?GPS alone gives an accuracy of
about +/–10m, but a number of free differential GPS systems (like
EGNOS or Omnistar VBS or Starfire SF1) add positioning information
to give +/–15-30cm. If you want better accuracy than that you can
pay a subscription to use the Omnistar XP or Deere Starfire 2
system, giving you an accuracy of roughly +/–10-20cm. And if you
want the best accuracy, you need a separate RTK base station. The
kit is more expensive but will give you accuracy down to +/–1-2cm.
All these figures will depend on your local conditions.
What is RTK?
The letters stand for Real
Time Kinematic. Nothing to do with old cinemas, but actually just a
technique for using a base station to add greater accuracy to the
signal you get from the satellites. Since the base station knows
its exact position, it can calculate a correction and boost the
standard accuracy from the GPS system sharply.
More importantly for many farmers is RTK's
repeatability. This means you can set an A-B line across the field
for a tramline and know you can return to that exact point year
after year. You can't do that with non-RTK GPS.
How do I translate that into accurate
fieldwork?
Good point. You could, in
theory, use this RTK signal to produce a frighteningly precise
lightbar and a very good tractor driver could get the benefit from
it. In practice, humans can't steer that accurately, so RTK set-ups
will invariably be used with full autosteer (where the system taps
into the steering hydraulic circuit) or the slightly less accurate
assisted-steer systems (where an electric motor physically turns
the steering wheel).
What are the drawbacks of RTK?
Cost is a factor. Even if you
have a tractor fitted with autosteer, you'll still need to pay
between £4000 and £10,000 for the base station. However, since the
base station can transmit its signal about 10km, you could share it
with a neighbour, though you'd need to have compatible systems on
your tractors.
And range is never guaranteed – trees and hills can
block the signal and leave you adrift, though manufacturers are
coming up with systems that keep you on the straight and narrow
until the signal returns. The other drawback is that if you are a
contractor or farm on more than one site, you'll have to cart the
base station with you.
Who makes all this kit?
The main players on the RTK
front are US firm Trimble (which also has a marketing agreement
with New Holland), Swiss camera and surveying equipment firm Leica,
Japanese Toshiba-offshoot Topcon (which has a marketing arrangement
with Agco) and John Deere. Claas works with Outback while one of
the well-established RTK pioneers is AutoFarm.
So will we all be using base stations
soon?
No, many farmers don't need
this sort of accuracy. And anyway, a new type of networked RTK
system has appeared in the last few months that may make some base
stations redundant.
It goes by various names – Trimble has its VRS Now
system and Leica has its Spidernet. Topcon and Deere are also
rumoured to have systems in the pipeline.
But the principle is the same – it does away with
the local base station using instead information from the Ordnance
Survey's 80-odd base stations around the UK and sending that signal
to the tractor or combine via the GPRS mobile phone network.
No more than a handful of units are out on farms,
but the system has potential.
Advantages?
Well, you don't need a base
station, for a start. And that means less hardware to get obsolete
as the years go by. It's also a relatively low-commitment way to
try RTK, particularly since some of the providers may decide to
offer three-month or six-month subscriptions.
Disadvantages?
You have to pay an annual
subscription fee (VRS Now will cost £1195/yr including SIM card and
all data charges) for the data and that fee is per tractor. So if
you want to use RTK with several vehicles, it might be cheaper to
have a single base station. Plus you need to enjoy a decent GPRS
mobile phone signal over the whole farm, which may not be the
case.