NMEA sentences; other GNSS

[Paul Theodoropoulos]

On 6/14/2019 17:07 PM, Gary E. Miller wrote:
> Yo Paul!
>
> On Fri, 14 Jun 2019 16:52:06 -0700
> Paul Theodoropoulos <paul at anastrophe.com> wrote:
>
>> Huh.  Seemed reasonable enough to me, other than that I'm unsure what
>> you meant with the last sentence, "but raning from SBAS hurts" due to
>> the typo...
> Yeah.  typo.  Saw that later.
>
> "raning" -> "ranging".
ah, thanks.
>
> The SBAS sats are in geo-stationary orbit (GEO).  So that a GPS does not
> have to search all 32 medium-earh orbit (MEO) birds to download the
> initial almanac.
>
> The extra distance to GEO, plus the added orbital uncertainty of GEO,
> mean that ranging (psuedorange, carrierpahse, and doppler) to SBAS
> are reduced accuracy compared to ranging the MEO birds.
>
> Now that GPS have 70+ receive channels it is faster to just download
> all the Ephemeris at start time.
Aha - that's good info, most of the sources I ran across on Father 
Internet were far too deeply technical for a mere mortal such as myself. 
This makes a lot more sense. Maybe you should rewrite the lede on the 
"GNSS Augmentation" argicle on wikipedia, har!
> Funny thing about that.  Recent discussion on NANOG to repeal that.
>
> Some feel it moves some of the burden from sloppy coders back onto those
> that want to interoperate with them.  Worth discussing over beer.

Interesting indeed. Yes, considering the massiveness of 
telecommunications, internet, protocols, channels - and abuse of same - 
perhaps being conservative in both what you send AND what you accept is 
the wiser path in the modern world. Back in the '70's in the nascent 
internet, the ethos was a lot more...I wouldn't say naive, but perhaps 
just 'innocent'.

But we digress.

-- 
Paul Theodoropoulos
www.anastrophe.com