Tomorrow, July 31, two satellites in the Wide Area Augmentation System constellation will be shut down by the government. The two satellites that have taken their place have been active and working for some time now, but the shutdown will have an impact on the differential correction accuracy of certain GPS receivers.

The two satellites, numbers 122 and 134, are scheduled to be shut off permanently at around 8:00 am EST. Many GPS receivers currently in service were configured specifically to lock into signals from those specific satellites, and must be reconfigured by the manufacturer. In the field, these units will not be able to achieve differential correction.

Some units manufactured by Midwest Technologies/TeeJet, Raven Industries, Trimble, and Hemisphere GPS are among those affected. For more information, click here.