On Nov 12, 7:18*pm, T wrote:
I've been told that the ADS-B out data includes GPS quality/
reliability information that comes from the WAAS receiver. Basically a
"trust me" code. Hopefully the cost of WAAS GPS recievers will come
down in costs as we approach 2020.

The Trig transponders have provision for setting the GPS data
integrity level in the configuration menus. If I had one I'd connect
any available GPS and set the integrity to LOW. I'm not asserting
that is either approved or legal.

From the installation manual:

"GPS System Integrity Level
An important metric for ADS-B ground system behaviour is the SIL or
System Integrity Level. It is intended to reflect the probability that
the GPS position source is providing erroneous information. A detailed
analysis of the contribution to system integrity is outside the scope
of this manual, and the installer may need to carry out a system
safety analysis to determine the best value to set. However, a
reasonable guideline might be:
Equipment
Transmitted Integrity Level
VFR only GPS or uncertified installation
Low
GPS installation certified for en-route and terminal IFR navigation
Medium
GPS installation certified with augmentation, such as WAAS or LAAS
High"

Andy