[time-nuts] GPS L2 CNAV health reporting changes

Bob kb8tq kb8tq at n1k.org
Fri Mar 9 09:38:40 EST 2018


Hi

The Trimble empire here (NetRS’s and NetR8) seem to be reasonably happy with everything. 
I haven’t dug into any of the data. They all show L2C tracking along like normal. 

Bob

> On Mar 8, 2018, at 9:23 PM, J. Grizzard <elfchief-timenuts at lupine.org> wrote:
> 
> 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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