Bob Pasker wrote:
i should have also added:

with FLARM, the aircraft move slowly, and they are all VFR, so having
relative position and altitude from a non-certified, low-res source is
still fundamentally useful for improving see-and-avoid (although not
necessarily for IFR separation)

On Tuesday, February 24, 2015 at 10:36:13 AM UTC-5, Bob Pasker wrote:
I wonder if the reason for requiring high-resolution TSO'd GPSs is that
ADS-B will be used for IFR separation and for fast-moving aircraft, so
high-resolution position and updates is an absolute requirement, a la fast-scan radar.

FLARM GPS *is* high resolution and highly accurate if it was not FLARM
could not possibly work. That separation between gliders in a thermal is
way less than what the FAA cares about using in the NAS. Some of the more
subtle GPS technical challenges were handled because FLARM knew what they
were doing, only worked with specific very well understood (to them) GPS
chipsets etc. Note that you never get to drive a FLARM with any old
external GPS source, but they provide a NEMA output as a convenience...

... and thank the FLARM folks for showing what is possible and helping the
FAA even get to TSO-C199. Now if anything ever comes from that we will have
to wait and see...