NMEA sentences; other GNSS

Gary E. Miller gem at rellim.com
Sat Jun 15 00:07:50 UTC 2019

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".

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.

> I mainly want to be conservative in what I send, and liberal in what
> I accept, with a tip of the fez to Jon Postel... :)

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.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
	gem at rellim.com  Tel:+1 541 382 8588

	    Veritas liberabit vos. -- Quid est veritas?
    "If you can’t measure it, you can’t improve it." - Lord Kelvin
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