[teqc] dumb clock questions

Andrew Miner minera at caliente.geology.cwu.edu
Thu Sep 1 14:48:41 MDT 2005


Jeff--

Can you clarify the first paragraph below?  I.e., which specific file
appears to have fangs? ("not the file from teqc, but the other one").

I still have not heard exactly how the .dat and non-teqc translated rinex
(all CAPS)  for BDZG and BOND came to be, but the source is a busy guy and
sometimes needs to be harassed repeatedly.

The file that came from Leica Spider is apparently being shipped to
Switzerland for further critique.

-------------------------------------------------------------
Andrew Miner				Ship (Fedex/UPS/DHL):
PANGA Data Center			CWU Hebeler Hall 108
509-899-1908 (cell)			10th and D St
509-963-1109 (fax)			Ellensburg, WA 98922
------------------------------------------------------------


On Tue, 30 Aug 2005, Jeff Freymueller wrote:

> Lou,
>
> I agree with you 100%. The danger with the rinex file that Andrew got
> (not the file from teqc, but the other one) is that the observables are
> not consistent.
>
> I tried to use the word "normal" or "typical" as opposed to "correct".
> I think the reason for the old Bernese converter's behavior dates back
> to the 1980s when Bernese estimated polynomial clock corrections and
> could not handle the sawtooth clock pattern that results from teqc
> +smtt. There were some objections raised from GIPSY users at that time,
> but we lost the argument at the time, and Werner's program in effect
> defined the standard.
>
> I would expect that any software ought to be able to handle the output
> of teqc +smtt, as long as it does not try to do any screening on the
> raw individual observables expecting them to be continuous. Any data
> screening that uses a clock-free linear combination, or that is done
> after an estimate of the clock error has been made and subtracted,
> should work on any flavor of RINEX file that has consistent
> observables.
>
> Jeff
>
> On Aug 30, 2005, at 11:45 AM, Lou Estey wrote:
>
> > Jeff Freymueller wrote:
> >
> >> [...] (This is because the original rinex definition of the clock,
> >> unfortunately, is not compatible with GIPSY's definition of the
> >> clock, and never has been - GIPSY requires the time tag to be the
> >> nominal measurement time as a perfect external clock would record
> >> it).
> >
> > Maybe this is a misconception, i.e. we all think that "correct" RINEX
> > uses the receiver time in the time tag -- probably because this is how
> > Berne (i.e. Werner Gurtner) did it for the original RINEX translators
> > for receivers with millisecond clock resets, i.e. Trimble .dat and
> > Ashtech B-files -- and GIPSY uses GPS time.  But from the RINEX spec:
> >
> > "3. DEFINITION OF THE OBSERVABLES
> >
> > GPS observables include three fundamental quantities that need to be
> > defined:
> > Time, Phase, and Range.
> >
> > TIME:
> >
> >   The time of the measurement is the receiver time of the received
> > signals.
> >   It is identical for the phase and range measurements and is
> > identical for
> >   all satellites observed at that epoch. It is expressed in _GPS time_
> > (not
> >   Universal Time)."
> >
> > Note the last line; the emphasis is mine.  (Of course, Werner was
> > really making
> > the point that the time tag be GPS time instead of UTC which would be
> > jumpy
> > due to insertion of leap seconds.)
> >
> > The main point is that there be consistency between time, phase, and
> > pseudoranges.
> > Therefore either:
> >
> > rx ms clk jumps in time tags (== receiver time), smooth phase and
> > pseudorange
> > (e.g. `teqc -smtt` output, Berne translation output)
> >
> > or
> >
> > smooth time tags (== GPS time), rx ms clk jumps in phase and
> > pseudorange
> > (e.g. `teqc +smtt` output, clockprep output, GIPSY input)
> >
> > are equally valid representations of the observables in RINEX.  They
> > use different
> > clocks though, which is why we can't use the observables in the former
> > representation
> > as input to GIPSY which is expecting smooth GPS time.
> >
> > I'm pretty sure that Bernese processing deals equally well with either
> > RINEX
> > presentation. What about Gamit, or the different manufacturers'
> > processing packages?
> >
> > --lou
> > _______________________________________________
> > teqc mailing list
> > teqc at ls.unavco.org
> > http://ls.unavco.org/mailman/listinfo/teqc
> >
> >
>
> Dr. Jeffrey T. Freymueller         Office: 907-474-7286
> Geophysical Institute              Fax:    907-474-7290
> University of Alaska, Fairbanks    Home:   907-479-3550
> PO Box 757320                      Cell:   907-322-7632
> Fairbanks, AK 99775-7320           email: jeff at giseis.alaska.edu
> URL: http://www.gps.alaska.edu/jeff/jeff.html
>
> Download Alaska GPS data: ftp://gps.alaska.edu/pub/gpsdata/
>


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