GPS Offers Something for Everyone

7/6/2013 7:00 AM
By Philip Gruber Staff Writer

LANDISVILLE, Pa. — Global positioning systems have come a long way since the early days when backpacking enthusiasts used handheld units to plot their winding paths on an otherwise blank screen.

Even motorists who use GPS to help them get in the correct lane, take the right exit and avoid traffic cameras will be surprised to learn how advanced these systems have become.

Dave Shaw of Binkley & Hurst and Ken Diller of Hoober showed off their companies’ products at the Farming for Success field day June 27 at the Penn State Southeast Research and Extension Center.

Only about five people in the standing-room-only crowd on the field day’s technology tour were currently farming with GPS, which uses satellites to pinpoint the exact position of an Earth-based receiver.

Shaw said the goal of GPS is to give farmers more information and more control on the go “so that you can make corrections on the go.”

For example, he said, a GPS system can detect when a few rows of a 16-row planter have stopped working. Without GPS, a farmer might not notice the problem until his crops were coming up with large gaps in the rows and replanting might be too late.

Speaking about the types of tools available, rather than the specifications (or prices) of particular screens, Shaw said that there are uses for GPS systems in every month of the year.

They can feed information to a yield monitor, map field conditions and boundaries, deploy foam row markers, provide row shutoff and assist in leveling a sprayer boom.

Some manufacturers are even looking at “down-to-the-nozzle” chemical control, he said.

Diller said that some sprayer-injection systems with GPS allow farmers to adjust the levels of up to five chemicals while in the field, saving a lot of time running back to the barn to change solutions.

GPS can also help when spraying around turns, adjusting so that the inside is not oversprayed and the outside is not undersprayed.

The systems can control the web and spinner speeds on dry box spreaders. Diller recommended this feature to people who spread near houses: The GPS can lower the spinner speed along property lines so that farmers do not spread chemicals into their neighbors’ backyards.

There are even several GPS-based apparatuses that can control the steering of tractors, combines and other farm machinery, Shaw said. They can be as simple as a friction bar that pushes the steering wheel or as complex as a mechanism built into the bottom of the steering column.

Auto-steering can be helpful when “you’re planting, you’re doing 18- to 20-hour days, and you’re coming home in the dark at 10, 11 o’clock,” he said.

Having the tractor take care of the steering can ensure field coverage and improve safety on those bleary-eyed slogs, he said.


Diller said that one of the most important questions for a GPS user might be, “Can I repeat that exact position?”

Different satellite systems offer different levels of precision.

Shaw said that most of the satellites used in the United States are from the WAAS (Wide Area Augmentation System) “constellation” of satellites owned by the federal government.

Diller said that a key thing to remember about GPS is that “it is a line of sight” system. Pennsylvania, he said, is “one of the most challenging places that I’ve seen” for farmers to use GPS because the fields are small and often surrounded by trees.

In a wide-open field, Diller said, a GPS may “see” eight satellites, but that might drop to three when tilling along the wooded edges of a field. Drawing on more satellites means greater data accuracy.

When the number of useable WAAS satellites drops, connecting to Russia’s GLONASS system, which offers an additional 21 satellites, can come in handy, Shaw said.

The WAAS system and John Deere’s StarFire systems are also of limited usefulness in very precise work, Diller said. Most satellites are drifting in space, and therefore their markings can drift 6 to 8 inches on either side of the intended line.

That might not seem too shabby for a machine hundreds of miles away in space, and it probably is good enough for spreading fertilizer or running a self-propelled sprayer, Diller said.

Some operations, such as planting seeds, however, require extreme precision. Potato growers need to know they are driving in the same place every time they are in their field or the cleats of their tires will clip the potato mounds, bruising and ruining their crops.

In those situations, Diller recommended using the RTK (Real Time Kinetic) positioning system. That system is land-based, which means its correction sources do not change position relative to the objects being mapped.


GPS is an extremely powerful tool for gathering information about one’s fields. The data is generally saved on a USB flash drive that plugs into the side or back of the screen. The farmer can then take the USB drive to a computer and look at detailed maps using specialized software.

“It can be very intimidating,” Shaw acknowledged, but he said the maps can provide a host of data that many farmers are probably already tracking by hand or in a computer spreadsheet.

Farmers do not have to come up with new, high-tech nomenclature to help them read the data for their different fields. Shaw suggested that farmers transfer the naming conventions they currently use for their fields to help them remember which one is which.

“The only thing I would warn is to be consistent, even to the point of capital letters,” Diller advised. “HOME” and “home” may register as different fields to the GPS, and though some software can merge those two files after they are created, it is easier to label things the same way from the start.

GPS can even help with regulatory compliance, Diller said.

Runoff regulations, especially in the Chesapeake Bay watershed, are stringent, and having GPS data on nutrient management can be useful in case of an environmental audit, he said.

A GPS can store information about where and how much manure a farmer has spread.

Field boundaries can be programmed the first time driving the field with the GPS. They can sometimes be added afterward on the computer or through data from a farmer’s crop management adviser, depending on what software is being used.

Wireless communication between the GPS in the tractor and the computer at a farmer’s house is “becoming more prevalent all the time,” Diller said.

WiFi can be helpful if a farmer finds the USB drives hard to use, and it prevents farmers from losing their data in accidents like a flash drive falling out of a pocket while they’re getting off the tractor.

Wireless can also sometimes save the hassle of home service calls because the network connection allows the dealer’s tech support to remotely access the GPS and fix problems.

The wireless signal will sometimes drop out, of course, just as it will for cellphone reception, Diller said. In that case, the GPS will continue to log data to the flash drive (if attached) and to the unit’s internal memory. The data can then be transmitted to the computer wirelessly or by the portable drive at the end of the day.

Nitrogen Sensing

Diller spoke at length about nitrogen sidedressing, an area where he said GPS use has grown a lot in the past five years. The goal, he said, is “real-time fertilizer placement.”

Nitrogen sensing started out with handheld chlorophyll meters that had to be clamped to the side of the plant. The meter emitted lights of three different frequencies that the human eye perceives as shades of red and yellow. The unit then used the reflected light to measure the mass and other attributes of the crop and calculate a normalized vegetative index number.

This number indicates differences in chlorophyll levels and gives crop scouts a prescription for how much nitrogen a plant needs.

Engineers have now improved the sensitivity of the sensors, alleviating the need for affixing them to the plant being measured, Diller said. The sensors now are mounted on the spray booms in the field, as many as eight per boom.

Each sensor controls a set of nozzles and adjusts the amount of nitrogen as the sprayer moves through the field, he said.

The GPS apparatus can also adjust the droplet size in the spray. Manufacturers say their products can accurately adjust sprayers at driving speeds up to 22 mph.

Diller cautioned that “the change is not instantaneous,” so driving faster may cause a slight lag in the spray adjustment compared with driving at slower speeds.

Diller said he expects that eventually GPS will be able to control each spray nozzle separately and may be able to distribute chemicals in doses individualized for every plant in a field.

The GPS also compiles the nitrogen data as a map. Diller showed a sample on a screen with bands of color indicating how much solution had been sprayed on each part of the field.

Diller said the impetus behind nitrogen sensing is not necessarily to save money on chemicals — the sensors may end up using more nitrogen — but at least the current technology is more precise than simply spraying a constant amount of nitrogen over the whole field.

The sensors replace guesswork with calibration for conditions in different parts of a field.

The increase in “field quality” is worth the investment in nitrogen sensing, Diller said. Of the farms using nitrogen sensing in his sales territory in the Midwest, he estimated the technology has not actually paid for itself on “less than 1 percent” of them.

Given the versatility of GPS technology, the various systems on the market offer the prospect of increased efficiency and productivity for almost any growing operation.

Diller said farmers should select GPS applications based on what processes they want to streamline and what information they want to collect about their fields.

“Is GPS for everybody? I would say, yeah,’ ” Diller said. “But a piece, not all of it.”

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