RTK and Beyond

Thigpen was knowledgeable enough about satellite-based positioning to know that he needed more than sub-metre accurate GPS before moving forward with his auto steer idea.

He explains, “Many golf courses include large tree canopies, hills and big slopes—all the kinds of features that cause trouble in the positioning world. I knew I’d need a large constellation of satellites that would include the GLONASS satellites to deliver a reliable, resilient golf course solution.”

When the GLONASS network became globally available and reliable in the civilian space around 2011, Thigpen was ready to market an auto steer sprayer system that was effective, reliable and affordable. He initially started with a GPS-only solution boosted by correction services such as the WAAS or by using Real- Time Kinematic (RTK) base stations with radios. While that solution worked great in an open field, he needed a more robust solution for common conditions such as under trees or in courses with significant elevation changes.

Subsequently, he teamed up with Ag Leader to use the Direct Command sprayer and SteerCommand auto steer systems, which both incorporate the NovAtel SMART6-L™ smart antenna—Ag Leader’s 6500 GPS System. Available to the market in 2012, the system is designed to support extended RTK baselines in excess of 20 miles utilizing the RELAY® CDMA or RELAY HSPA cellular radio modules.

Today, Thigpen’s auto-steering sprayers, spreaders and mowers support WAAS/ EGNOS, GLONASS, TerraStar-C as well as RTK networks. In addition, they provide builtin cell modems for access to CORS and NTRIP networks or base stations with RELAY 400 or RELAY 900 rover functionality.

“With the 6500, we have reliability, faster processing, better signals, and a system that works in shaded areas with less signal loss,” he says. “Creating repeatable data is one of the many advantages to GPS spraying using RTK navigation. Many of these golf courses have a $150,000 USD or more fertilization budget. Automated sprayer systems equipped with GPS can cut 20% or more from that budget in the first year.”

On the Course

Clark Weld, Superintendent for Hidden Creek Golf Club in Egg Harbor Township, N.J., is one of the first golf course superintendents to take advantage of GPS-enabled sprayers.

“There’s no skipping or overlapping during the application. We’ve virtually eliminated the chance of operator error. The GPSenabled auto steer sprayer system paid for itself in less than 3 years,” says Weld.

The Ben Crenshaw, Bill Coore-designed course was constructed in 2002. The 125-acre course consists of bent grass, a lot of rough, natural areas and, if not controlled, a lot of weeds.

Weld says, “We were using one of the old sprayers from another course and it wasn’t working very well, very inefficient. We needed a new sprayer. I have some farming friends who swore by the GPS technology for managing crops. At around the same time, I ran into Marcus at a turf management show where he was demonstrating his new auto steer sprayer system with tip control.”

He bought one 300-gallon Toro sprayer in winter 2012 as well as two GPS systems (one for the new sprayer and one for the old sprayer) with an RTK base station. In the first year, Weld was able to reduce his chemical budget from $125,000 to $80,000 USD.

Weld says he knows exactly how much product is applied per acre so there are no longer surpluses or shortages at the end of an application.

Weld has since moved the auto steer system to a fairway mower. He confirms, “The auto steer system is almost a plug-and-play device that we can shift from one piece of equipment to another. So we tried it on a fairway mower—and saved two hours in mowing time the very first time. That may not seem like a lot, but when added up over the course of a week, a month and a year of mowing, that’s a lot of savings in fuel and equipment wear and tear.”