Here is the actual warning from NOAA. I've added emphasis. Note that they warn of "loss of lock." In other words, GPS
is rendered unusable - you might as well turn it off. That's quite a bit worse than a "fraction of an inch" error mentioned above.
Aviation GPS receivers
certified for instrument approaches are required to have Receiver Autonomous Integrity Monitoring (RAIM) because it's acknowledged that GPS
can undergo disruptions.
The sky isn't falling, but the Sun can toss us some pretty impressive stuff. Those who think they can rely entirely on GPS all of the time are deluding themselves. It's best to always have a Plan B.
Message Code: WARK07
Issue Time: 2012 Mar 09 1146 UTC
EXTENDED WARNING: Geomagnetic K-index of 7 or greater expected
Extension to Serial
Valid From: 2012 Mar 09 0700 UTC
Now Valid Until: 2012 Mar 09 1500 UTC
Warning Condition: Persistence
NOAA Space Weather
Scale descriptions can be found at
NOAA Space Weather Scales
Potential Impacts: Area of impact primarily poleward of 50 degrees Geomagnetic Latitude.
Induced Currents - Power system voltage irregularities possible, false alarms may be triggered on some protection devices.
Spacecraft - Systems may experience surface charging
; increased drag on low Earth-orbit satellites and orientation problems may occur.
Navigation - Intermittent satellite navigation (GPS) problems, including loss-of-lock and increased range error may occur.
- HF (high frequency) radio may be intermittent.
Aurora - Aurora may be seen as low as Pennsylvania to Iowa to Oregon