Darrell Smith, Farm Journal Conservation & Machinery Editor
Using auto-guidance is easy. But purchasing your first RTK auto-guidance system (real-time kinematics, with sub-inch, repeatable accuracy) takes a little more planning than merely letting go of the steering wheel.
“Define your objectives before you buy,” says University of Kentucky agricultural engineer Scott Shearer. “Do you want to perform subsequent operations based on the same A-B line? Do you need relative accuracy or absolute accuracy? Relative accuracy is okay for tillage and spraying, but you need absolute accuracy to run in the same wheel tracks, and if you have longer fields. In some applications, you will want to consider adding either active or passive implement guidance.”
Implements don’t always follow directly in the tractor tracks, Shearer explains. “Even if you hold tractor accuracy to 2.5 cm, or 1”, we typically see implement errors up to 10 times that amount,” he says. “The problem becomes worse with low-draft implements. Planters, whether drawn or fully integral, tend to wander even on flat ground.”
As you consider an RTK system, “look a few years into the future, at what you may want to do,” advises Kyle Collins, a marketing representative for John Deere Ag Management Solutions. “Look for a dealer who offers good support and who will be in the game for the long term.”
Before you buy, ask your dealer if you will have access to an RTK network, says Collins. If you farm in an area without a network signal, you will have to use a portable base station. Portable stations must be in place for 24 hours to establish an absolute reference.
“If you don’t give a base station enough time to lock in absolute coordinates, you can wind up as much as 15' off your original A-B line,” says Jim Ellis, who farms with brothers Mike and Bob in Shelby and Henry Counties, Ky.
The Ellises’ have another solution. “In planting season, time and people are too scarce to have to continually move the base station from field to field,” says Jim. “So we are placing several base stations—probably a total of three—on towers, to create a local network. When we lose signal from one station, we can simply change the channel on our vehicle receivers to match the channel of the next base station, and operate off that one.”
In some situations, the Ellises plan to install a repeater to extend the base station’s signal. “By next spring, we expect to be pretty much bug-free,” says Jim.
As you narrow down your guidance system choices, “talk to other farmers who have used the equipment you’re considering,” says Ellis. “Go ride in the cab with a friend who is using it, someone you can call in the future if you have questions.
You’ll simplify your life by buying a monitor and receiver for each machine, says Clay Mitchell, who farms near Buckingham, Iowa. “It’s a headache to transfer monitors and receivers between vehicles,” he says. “Many seasoned RTK users now view those components as integral parts of a vehicle, just like a steering wheel. And the components have become more affordable.”
“After you buy a system, go out to the field in the winter and learn to use it,” Ellis continues. “And don’t be afraid to call the technical assistance phone number, if you need help.”
But Ellis is reassuring. “Learning to use an RTK guidance system isn’t that hard anymore,” he says. “A lot of the early quirks have been ironed out.”
For More Information
A worksheet to help you evaluate the economics of precision farming techniques on your farm.
John Deere Ag Management Solutions’ precision-ag site
You can email Darrell Smith at dsmith@farmjournal.com.
