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
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
A GAME OF INCHES