A new report from John Deere provides perhaps the strongest documentation to date that deploying the controversial LightSquared satellite and land-based cellular communications network will dramatically interfere with agricultural GPS navigation systems.

In a letter accompanying the report, sent to the Federal Communications Commission (FCC) in late May, Deere said that deploying the LightSquared network “will create massive interference” for Deere’s StarFire system, as well as other similar systems, “risking serious harm to the U.S. agriculture industry.”

The report noted that in simulated tests, LightSquared transmissions interfered with GPS signals as far away as 22 miles from the transmitter. Furthermore, it said there are no effective work-arounds to mitigate the interference. LightSquared has indicated it could construct up to 40,000 ground transmitters as it builds out its network.

The Deere report comes at a critical juncture for the LightSquared network, which received a tentative license from the FCC in January. In issuing the tentative license, FCC required LightSquared to work with the GPS industry to resolve the issue over whether its transmissions would interfere with GPS signals. The deadline for a joint report from LightSquared and the U.S. Global Position System Industry Council is today (June 15, 2011).

For additional coverage on the Deere report and a link to a downloadable copy of the report, go to www.gpsworld.com.