In a place nicknamed The Farm, it seems fitting that folks would be working on tractors. But this is no ordinary checkerboard of fields – it happens to be located in the Silicon Valley. So, as you might expect, the tractor is not very ordinary, either.
This intersection of agriculture and technology is at Stanford University, where a band of researchers are developing a way to steer John Deere's finest with the help of satellites. The idea of driving a tractor with the help of Global Positioning System satellites was born of a need to develop something with implications beyond basic research, said graduate student Michael O'Connor. The result is this joint effort between the university and the nation's biggest farm-equipment manufacturer.
Through this work, O'Connor was surprised by what he found among the farmers he and his colleagues contacted. "Farmers are very heavily involved in GPS technology," he explained. "They already use GPS to plot contour maps of their fields and to do imaging of the growth patterns of their fields."
So the farmers proved a ready market for a remote-driven tractor, O'Connor noted.
Tractors in the research were outfitted with receivers and antennas derived from an aircraft landing system developed by the university's aeronautics and astronautics department. These sensors achieve their accuracy with the help of a little error correction.
The system is an enhanced type of differential GPS. Like many DGPS systems, the Stanford test cross-coordinates the GPS satellite's signal with a ground-based reference signal broadcast by a stationary antenna, which knows its precise position. But where DGPS may use stations that are relatively far from the object to be controlled, the Stanford/Deere system places the stationary antenna much closer to the source, allowing the tractor to receive the satellite and ground station data simultaneously, said Terry Pickett, manager of engineering for precision farming at Deere and Company.
The ground station reconciles its own received GPS data with its known position and sends a differential signal - the difference between the known position and the GPS-calculated coordinates - to the antenna on the tractor. With this signal, the tractor can correct the directions it is receiving from the sky.
The resulting navigation system can tell farmers precisely where their tractors are along a path to within one or two centimeters. By contrast, DGPS might determine location within a meter, Pickett noted.
Testing this system pushed The Farm to its land limits. "The longest field we have is 100 yards – we had to turn around a lot," O’Connor explained. So the Stanford researchers looked for greener – and bigger – pastures on John Deere's test fields in Arizona.
On these fields, researchers were able to put the system through its paces, and even staged a contest to see how the satellite-guided system matched up against an experienced tractor steersman. The scientists examined how closely the tractor maintained its course in test runs that were as long as a half-mile in one direction. The GPS system proved to be more accurate. The driver veered from the path by an average of four inches, while the GPS-steered tractor wavered by only an inch.
This accuracy may give farmers an economic edge, as a GPS-steered tractor can do its job at times when mere mortals can't – at night, in the fog, and during dust storms. Times of low- or zero-visibility can hamper crucial operations such as planting and harvesting that must happen within a narrow range of time, lest crops and profits be lost. But with a GPS system, signals can reach the tractor through fog and nightfall, and thus make farms more efficient.
But there are still bugs to be worked out, Pickett explained. Deere's work may one day lead to an automated tractor system, but this system and any future iteration must be "bulletproofed" to sense people and animals, and whether it is operating correctly. It should be able to shut down automatically in the wake of obstacles or malfunctioning, he said.
It also has to be within the grasp of Deere's customers. "It's a very impressive concept ... it's too expensive for most of our customers right now," he said.
