On Thursday, October 29, 2015 at 11:10:28 AM UTC-7, Dave Nadler wrote:
On Thursday, October 29, 2015 at 1:30:07 PM UTC-4, Jonathan St. Cloud wrote:
I have three gps' in my bird...

Shocking. Time to upgrade. Minimum equipment:

PowerFlarm
Logger#2
AHRS w/GPS
Personal tracker
406ELT w/GPS
iPhone w/GPS

Obviously you're way behind!
And probably not enough batteries either ;-)

I have 5:

Air Avionics ISU
PowerFlarm
iPhone 6+ used for iGlide
iPhone 5s used for cell phone
Delorme Inreach

Nevertheless, in the unlikely event of an EMP or the more likely event of GPS interference/unavailability, none will work.

But I have never flown a compass course in a glider. In VFR, you don't need it; in IFR, it is insufficient without an AHRS, and then you don't need it. Conclusion: you don't need it.