[teqc] helpful tip of week 1920

Lou Estey lou at unavco.org
Wed Oct 26 10:22:49 MDT 2016


This week's tip: the '-M.dec' and '-N.dec' options

Hopefully you remember the tip from five weeks ago that covered the '-O.int' and '-O.dec'
options.  Recall that the primary job of '-O.int' is to supply a value for the optional
'INTERVAL' header line in a RINEX GNSS observation file.

There are no INTERVAL header lines in RINEX meteorologic or navigation files, so there is
no need for '-M.int' or '-N.int' options, and the latter does not even exist.  (You will
note there there is a '-M.int' option, which sets the expected met pack sampling interval,
and this does have, if used, a single and now obscure use when reading Ashtech XDR records
in the Ashtech stream format that are either for met or other external event data.)

There are, however, the '-M.dec' and '-N.dec' options, which have been in teqc basically
since the beginning, completing the symmetry with '-O.dec'.  However, the '-N.dec' option
doesn't have any underlying code which really does anything and I can't imagine a case why
one would need to decimate navigation messages, but if a case ever comes up, the stub is
there for getting started.

But, the '-M.dec' actually can be used for decimating meteorological observation epochs.
There's one problem though.  Often met epochs do not occur exactly when you expect them.
Example, here's a RINEX met file where the met sample interval was 5 seconds:

...
      3    PR    TD    HR                                    # / TYPES OF OBSERV
...
  10 12  6  0  0  1 1007.1   12.8   92.1
  10 12  6  0  0  6 1007.1   12.8   92.1
  10 12  6  0  0 11 1007.2   12.8   92.1
  10 12  6  0  0 16 1007.1   12.8   92.1
  10 12  6  0  0 21 1007.0   12.8   92.0
  10 12  6  0  0 26 1007.1   12.8   92.0
  10 12  6  0  0 31 1007.2   12.8   92.1
  10 12  6  0  0 36 1006.9   12.8   92.1
  10 12  6  0  0 41 1007.0   12.8   92.1
  10 12  6  0  0 46 1007.1   12.8   92.2
  10 12  6  0  0 51 1007.1   12.8   92.2
  10 12  6  0  0 56 1007.0   12.8   92.2
  10 12  6  0  1  1 1007.3   12.8   92.3
...

So, instead of the epochs occurring at 0, 5, 10, ..., 55 seconds into each minute, they
are 1 second later (due probably to query time of the met pack and the receiver recording
the met strings).  If you were to try to decimate to an epoch every minute using '-M.dec 60',
you would end up with zero met epochs in the output because teqc will be looking to
output only those epochs that occur at 0 seconds -- of which there are none.

It turned out that there was also an undocumented offset option with '-M.dec' as well,
but even if set on the command, it was not doing anything under the hood.  I realized
this problem five weeks ago when I was telling you about the undocumented offset option
with the '-O.dec' option.  This was fixed on 26 Sept 2016 -- and that fix is in the
2016Oct18 beta version you were told about last week.  So, now using '-M.dec 60:1' on
the above with the fixed teqc, the output is:

...
      3    PR    TD    HR                                    # / TYPES OF OBSERV
...
  10 12  6  0  0  1 1007.1   12.8   92.1
  10 12  6  0  1  1 1007.3   12.8   92.3
  10 12  6  0  2  1 1007.1   12.8   92.3
  10 12  6  0  3  1 1007.1   12.6   92.0
  10 12  6  0  4  1 1007.2   12.5   92.0
  10 12  6  0  5  1 1007.3   12.5   92.3
  10 12  6  0  6  1 1007.2   12.4   92.0
  10 12  6  0  7  1 1007.5   12.3   91.9
  10 12  6  0  8  1 1007.3   12.2   91.9
  10 12  6  0  9  1 1007.5   12.3   92.2
  10 12  6  0 10  1 1007.5   12.2   91.8
...

... outputting an epoch every minute, which is what we wanted for this example.  There was
another coding correction made so that you want use '-M.dec 60s:1' or '-M.dec 1m:1' to do
the same operation as '-M.dec 60:1'; '-M.dec 1m:1', of course, meaning "decimate at 1 minute
intervals with an offset of 1 second".  Like with '-O.dec', units of seconds are assumed
unless a time unit modifier is included.

Happy teqc-ing!

cheers,
--lou

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Louis H. Estey, Ph.D.              office:  [+001] 303-381-7456
UNAVCO, 6350 Nautilus Drive           FAX:  [+001] 303-381-7451
Boulder, CO  80301-5554            e-mail:  lou  unavco.org
      WWW:  http://www.unavco.org   http://jules.unavco.org

"If the universe is the answer, what is the question?"
                                                -- Leon Lederman
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Past helpful tips:

week 1894: using teqc config files - http://postal.unavco.org/pipermail/teqc/2016/002067.html
week 1895: qc of high-rate data - http://postal.unavco.org/pipermail/teqc/2016/002071.html
week 1896: UNIX/Linux shells for Windows - http://postal.unavco.org/pipermail/teqc/2016/002072.html
week 1897: '-' vs. '+' teqc options - http://postal.unavco.org/pipermail/teqc/2016/002076.html
week 1898: auto-identification of formats - http://postal.unavco.org/pipermail/teqc/2016/002092.html
week 1899: auto-identification vs. format flags - http://postal.unavco.org/pipermail/teqc/2016/002096.html
week 1900: square brackets in options - http://postal.unavco.org/pipermail/teqc/2016/002105.html
week 1901: using option '+mds' - http://postal.unavco.org/pipermail/teqc/2016/002108.html
week 1902: qc results w/ problematic nav messages - http://postal.unavco.org/pipermail/teqc/2016/002113.html
week 1903: '-no_orb[it]' and '-no_pos[ition]' options - http://postal.unavco.org/pipermail/teqc/2016/002115.html
week 1904: '-week' option - http://postal.unavco.org/pipermail/teqc/2016/002117.html
week 1905: using '+bcf' for XYZ/geodetic conversion - http://postal.unavco.org/pipermail/teqc/2016/002126.html
week 1906: the '+v[erify]' option - http://postal.unavco.org/pipermail/teqc/2016/002128.html
week 1907: '+C2', '+L5', "+L6', '+L7', '+L8', and '+all' options - http://postal.unavco.org/pipermail/teqc/2016/002130.html
week 1908: no doppler shortcut; RINEX L2 - http://postal.unavco.org/pipermail/teqc/2016/002131.html
week 1909: using paths w/ file names - http://postal.unavco.org/pipermail/teqc/2016/002132.html
week 1910: the (un)importance of file names - http://postal.unavco.org/pipermail/teqc/2016/002133.html
week 1911: notices, warnings, and errors - http://postal.unavco.org/pipermail/teqc/2016/002134.html
week 1912: the '-max_rx_SVs' option - http://postal.unavco.org/pipermail/teqc/2016/002137.html
week 1913: the end of '++igs' and '+igs' - http://postal.unavco.org/pipermail/teqc/2016/002140.html
week 1914: splicing together RINEX files - http://postal.unavco.org/pipermail/teqc/2016/002144.html
week 1915: using '-O.int' and '-O.dec' - http://postal.unavco.org/pipermail/teqc/2016/002145.html
week 1916: '+doy' option - http://postal.unavco.org/pipermail/teqc/2016/002146.html
week 1917: '-tbin' and '-ast' options - http://postal.unavco.org/pipermail/teqc/2016/002152.html
week 1918: mp12 RMS before/after Oct 2013 - http://postal.unavco.org/pipermail/teqc/2016/002158.html
week 1919: the global windowing options - http://postal.unavco.org/pipermail/teqc/2016/002159.html




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