I got a message from the Swiftnav support folks yesterday (I have a
piksi multi amongst my little fleet of GPSen) because they had an
emergency firmware patch to their kit because of a change in the L2C
signal was giving them issues. (Props to them for getting a firmware
update out in ~12 hour, too)
After a little bit of inquiring, it looks like what happened is that
yesterday, the L2 CNAV message started marking all of the L1 signals as
unhealthy. If a device actually listens to this health signal
(apparently their GPS did), suddenly most GPS satellites become unusable
(with the only remaining ones being ones that aren't transmitting an L2C
signal).
(According to NANU 2014039, you shouldn't be using those health
indicators, though it does also say that the L1 health indicators would
all indicate "healthy", so this seems to be a departure from their
stated plan.)
Anyhow, probably doesn't affect anyone here, but I thought it was
interesting. Sadly, I can't see what's actually being transmitted, since
my only pieces of kit that can decode L2C are my piksi (which won't give
me raw NAV/CNAV, and they apparently have zero interest in adding that
functionality), and the Novatel OEM628 that I picked up off eBay last
year ... which crashes every 20 or 30 minutes if I ask it to decode L2C.
Argh.
(Maybe u-blox's upcoming kit will be affordable(ish) and have good raw
CNAV output... I can hope, right?)
-j
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