GPS BROWNOUTS could become more frequent in the decade ahead. Why? Delays in developing replacements for the 30 or so aging GPS satellites currently in orbit are cited as the reason, according to a U.S. Government Accountability Office (GAO) report issued in April last year.

Currently, brownouts occur for an hour or two at a time many times a year, depending on the location. Most farmers don't notice them, because they occur outside the peak GPS usage window, notes Matt Darr, Iowa State University.

By some estimates, almost half of current GPS satellites are at or approaching the point where the failure of a single critical system could take it out of commission.

If the number of GPS satellites drops below 24, guidance from lightbars and autosteering systems will be affected. This is particularly the case when farming in areas with trees or other obstructions that limit satellite visibility.

“You have to have a minimum of four satellites to generate a GPS position for use with any precision ag product,” Darr says.

This problem is minimized with the latest dual-frequency navigation systems, which can access the Russian GLONASS satellite system in addition to GPS, Darr says. — David Hest