[time-nuts] GPS PRN vs SV...??
Magnus Danielson
magnus at rubidium.dyndns.org
Sat Feb 9 09:13:39 UTC 2008
From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
Subject: Re: [time-nuts] GPS PRN vs SV...??
Date: Sat, 09 Feb 2008 21:57:57 +1300
Message-ID: <47AD6B15.7090701 at xtra.co.nz>
Hej Bruce,
> > > It actually does not clearly states that in my documentation. It
> > > contradicts itself!
> > >
> > > Byte Item Type Value Meaning
> > > 2 Sat PRN # UINT8 0 Data that is not satellite ID-specific
> > > 1 to 32 Satellite PRN number
> > >
> > > Byte Item Type Meaning
> > > 4 SV number UINT8 SV PRN number
> > >
> > > The field SV number (which is what we are looking for) is said to have the
> > > meaning of SV PRN number.
> > >
> > >
> >
> Perhaps Trimble's SV number = GPS SVID (as defined on page 8 of the GPS
> Interface control document)
> for SVs: SVID = PRN#.
Yes, but SVID isn't SVN, which may be the cause of confusion.
Actual SVNs isn't meaningfull for normal GPS users and bears no meaning to the
receivers, where SVID and PRN# is the important things.
> Perhaps all is explained, if one notes that the SVID's described in the
> GPS Interface Control document are identical to the SV PRN# except when
> SVID is used to differentiate between data pages.
> PRN# can be as high as 37 (but not for SVs which are limited to a
> maximum of 32).
It would appear that during normal operation PRN# is set to the SVID. There is
actually a SVID to PRN# mapping provided, but the SVID range isn't free enought
to hold SVN numbers.
> I didnt find any mention of the SVN # in the Interface Control document
> so maybe it isnt broadcast (or at least it isnt publicly available via
> GPS messages).
Looking into IS-GPS-200D I am inclined to agree.
> The Motorola M12+ user manual indicates that the SVID is used in some
> messages.
>
> Has anyone dumped Thunderbolt report packets 0x58 to a text file?
Requesting data for PRN# 1-32 and hex-dumping the result would be of
interest.
Cheers,
Magnus
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