• Dusty Sonnenberg

Updates needed in older WAAS GPS guidance systems

Many farmers who use GPS equipment use the free Wide Area Augmentation System (WAAS) signal. Many of the older light bars and basic steering systems that are not subscription-based correction signals fall into this category. The satellite settings for these units were typically set up when first installed and then forgotten about.

Unfortunately, during one of the busiest times in the planting season for much of the corn belt, one of the satellites will be decommissioned, and a different one will be made available. This change in satellites will cause the GPS equipment to not find the signal needed and therefore not be able to guide until a change is made in the settings to direct it to find the new satellite.

Effective May 17, 2022, WAAS PRN 138 satellite were decommissioned and ceased transmissions. A new satellite, PRN 135, replaced the current WAAS PRN 138. The new satellite is the Galaxy 30, located at 125 degrees west longitude.

This also means for farmers that Global Navigation Satellite System (GNSS) receivers that have been manually set to receive corrections from PRN 138 will not be able to obtain a differential correction. Instead, a different PRN will need to be selected. GNSS applications use GNSS receivers to collect position, velocity, and time information.

Each company/brand is slightly different in changing the settings. “The user simply needs to go into the settings and, in effect, turn off PRN 138 and turn on PRN 135, so the receiver knows what to look for. Many receivers are set for autotuning,” said Matt Liskai of Green Field Ag. “The hope is that for these systems, no changes will be needed. However, if a system is not set up to automatically tune, changing the settings is not difficult. There are several tutorials available online, and it is as simple as a couple of button pushes under the settings and GPS tabs to turn on the PRN 135 satellite.”

This change only affects WAAS users. If a farmer is using a subscription signal and running John Deere SF-1, SF-2 or SF-3, Trimble RTX, RTK, Outback Atlas, or Raven GS, they won't be affected.

If a farmer uses a GNSS receiver, they should manually change WAAS PRN settings to one of the operational satellites 131, 133, 135, or choose "Automatic" to receive GPS corrections.

To find easy-to-follow videos showing how to make the change on various monitors, check out the following information from the Sunrise Cooperative precision ag team.


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