GPS systems are getting more user-friendly and an increase in the number of satellites will make these systems more reliable, according to North Carolina State University Extension Farm Equipment Systems Specialist, Gary Roberson.
GPS currently comes in three flavors he notes: autonomous, differential, and RTK. If you take away the two correctional features, or enhancements, there is not a lot of difference between the differential system that most farmers use — the RTK correctional system and the basic hundred dollar autonomous system that can be purchased at most any electronics store.
“What we’ve done is to take the basic structure and add these special features to them,” Roberson says. “Today, there are millions of users worldwide and the simplicity of the basic system makes its future in agriculture very bright,” he adds.
GPS is a military satellite system that allows civilians to tap into a small portion of it for commercial use. Every year the government and private enterprises send up more and better satellites, making existing systems much more reliable, the North Carolina State professor says.
WAAS (wide area augmentation system) is the most common system that farmers use. In the summer of 2007 many of those WAAS systems didn’t work too well. The reason, Roberson says, is that new satellites were launched this past summer and though some of the new technology carried by these satellites was self-correcting, some required minor tweaking of current equipment.
Once corrections were made, the older WAAS systems worked better, he says.
RTK (real time kinematic) systems require a base, or access to somebody else’s base. RTK systems are line of site with limited range — 6-8 miles. The good news is that a number of very good RTK networks are being developed by equipment dealerships. These subscription services are being offered to growers.
By subscribing to one of these subscription services, growers can reduce the price of a RTK system from about $30,000 to $15,000. These subscription services typically cost from $500 to $700 a year and provide accuracy of plus or minus one-fourth inch.
“Another option is to have GPS correction delivered by cell phone. Surveyors in North Carolina already use a RTK network that covers about 70 percent of the state. Surveyors pay a one-time $500 fee to tap into the network, then pay whatever is their monthly cell phone data plan service,” Roberson says.
“We don’t see that in agriculture because our corrections are delivered by short-range radio. These GPS receivers are coming from the same company — the only difference in the equipment used by surveyors and farmers is the box that contains it. If we can convince these companies to deliver information via the cell phone, it will revolutionize the way agriculture uses GPS,” Roberson says.
Growers who have already invested in an RTK system with a base unit can easily reconfigure their system to tap into one of these subscription services. The corrections are identical, but it would give a grower some insurance should either of the systems go down.
The cost of all GPS equipment is coming down. Compared to the rising cost of fertilizer, diesel fuel and a plethora of other input costs, GPS equipment that can reduce the use of, or make the use of these costly inputs more efficient, is a good investment in the future.