In the folk tale The Emperor's New Clothes, a child dared to mention the unmentionable. Terry Anderson, Autonomous Tractor Corporation, is also mentioning the unmentionable. Could GPS be the weak link in precision agriculture?

"GPS is being used in ways never intended," said Anderson. "It wasn't meant to be mobile, and it has a number of weak spots. The Crookston, Minn., area was without GPS for three days this past spring when solar flares ionized the atmosphere. Farmers have told me they can't depend on GPS when they get close to buildings or around water towers. If they depend on RTK, they are secondary users. If emergency services need the bandwidth, secondary users are locked out."

Anderson has strong agricultural roots, but he is a relative newcomer to industrial agriculture. However, his credentials give his concerns added validity. The consulting engineer has built his career advising multi-national, non-agricultural companies on the use of technology. Over the past 14 years, he and his 47-person web of technical associates have turned their attention to building a better tractor. Introduced at the 2012 Big Iron Show in Fargo, his prototypes left farmers scratching their heads, but intrigued. More than farmers were intrigued as well.


Still in development, Spirit is a completely autonomous tractor without so much as a driver's seat. Looking like a block on tracks, Spirit is powered by twin 200 horsepower gensets with electric drive wheel motors, 10 computers, sensors galore, touch-pad control screens on either side, redundancy throughout, but no GPS.

"We developed our Area Positioning Systems (APS) using radio beacons," said Anderson. "We use four transponders set around a field with two on the tractor. We've tested the range, and they easily cover a two-mile distance, more than enough for a 2,500-acre field. One set of four static transponders can control up to 16 autonomous units in the same area."

Is GPS the Emperor's New Clothes?Alternative positioning systems to GPS are not new. Radio and laser combination transponders have been used for 20 years in the North Atlantic to control ships servicing the oil rigs so they don't hit the platforms. Other systems are used in open-pit mining. Anderson is using 150 MHz frequency transponders without lasers. The transponders on the tractor constantly exchange signals with the static transponders for position identification and recording. The computer charged with location constantly compares its position to the positions of the static transponders.


Anderson sees multiple advantages with APS, including sub-inch and repeatable accuracy as well as ease of use. He expects that when the job is done, field units would be removed, used elsewhere and replaced when needed. However, the anticipated price tag of $600 per set or $100 per transponder opens the door to permanent installations.

"We are close to getting them down to a single integrated chip, a solar panel and an enclosure," said Anderson.

Although cost and simplicity are attractive to Anderson, it is the reliability that drove his decision to bypass GPS. As a proponent of autonomous field equipment, he recognized that there can be no interruption of signal. Whether from a safety/liability standpoint or the time sensitive nature of farm work, waiting for a solar flare to end is not an option. Having RTK shut down, even temporarily while an accident or other emergency takes place in an area, likewise is not an option.

Anderson is confident that APS, whether introduced by his company or others, offers an attractive and superior option to GPS and RTK. The proof is in the interest he has received.

"Trimble, Topcon and Raven all want to know more about our system," said Anderson. "So do farmers, like the one who recently told me he uses GPS on his entire farm, except for 30 acres near his buildings. Agriculture has adapted GPS to its needs, but there are problems with it."