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There has been a lot of talk lately of self-driving cars,

but farmers have already been making good use of self-

driving tractors for more than a decade—in part due

to a partnership between John Deere and NASA’s Jet

Propulsion Laboratory (JPL) on GPS receivers.

The story, featured in the latest issue of NASA Spinoff,

coming out Dec. 5, starts with GPS which was still new in

the mid-1990s when John Deere, based in Moline, Illinois,

began using it for precision agriculture. The company

combined GPS location data with readings from sensors

on a harvesting combine to determine the crop yield on

different parts of the field.

Such information can help farmers allocate future

resources and determine which seed varieties and

management practices are the most productive. But John

Deere wanted to go a step further, to create a system




John Deere


Tractors Drive Themselves

that could actually guide the tractor autonomously. The

challenge was that uncorrected GPS can be off by up to

about 30 feet due to data errors, drift in the GPS satellites’

internal clocks, and inaccurate orbital parameters.

Scientists at JPL, where the first global tracking system for

GPS satellites had been developed, were already working

on a crucial ingredient: a tool to stream satellite tracking

data in real time via the Internet, rather than collecting it

intermittently by phone lines.

Thanks to a major funding infusion from the Federal

Aviation Administration, which wanted to provide pilots

with reliable GPS data, the JPL team was able to develop

the necessary software, says Yoaz Bar-Sever, who was

supervisor of the Orbiter and Radiometric Systems group

at JPL at the time.

It was “a breakthrough capability,” recalls Bar-Sever. “We

were approached by many companies” — one of which

was John Deere

John Deere had been working on its own technology

for correcting GPS signals in cooperation with another

company, NavCom, which John Deere later acquired. By

2003, the company developed a self-guidance system

that was accurate down to an inch or so.

However, the system wasn’t entirely reliable, as its radio

signal could go down or be lost behind a hill, says Terry