[teqc] helpful tip of week 1919

Lou Estey lou at unavco.org
Tue Oct 18 07:16:49 MDT 2016


This week's tip: the '-st', '-e', and associated delta window options

Again, these windowing options are pretty well covered in the original HTML tutorial
in Section 13:
http://www.unavco.org/software/data-processing/teqc/tutorial/tutorial.html#sec_13

The purpose of this tip is to give some pointers and hopefully clear up a few
misunderstandings.

First, the start and end times, whether explicitly set (with '-st' and/or '-e'
and/or a delta option) or whether implicitly set from the beginning and end
times of the supplied target file(s), are (or should be) inclusive.  In other words,
if the observation data has an epoch at the start or end time, this epoch should be
included in whatever process teqc is doing.  This, then, is a distinct difference
from the '-tbin' option with its delta.  For example, let's say the input
starts at 00h00m00s, has 30-second sampling, and has a last epoch at 00h00m00s
the next day. Then using these two methods:

+dh 24
-tbin 24h <filename_prefix>

will yield different results for what makes up the last epoch of the file.  Using
'+dh 24' the last epoch will be at 00h00m00s of the second day, but using '-tbin 24h'
the last epoch of the first observation file will be at 23h59m30s of the first day.
Also, using just '-tbin 24h' in this example will result in a second observation file
with just one epoch at 00h00m00s of the second day, although one could eliminate that
second one-epoch file by using '+dm 1439.5 -tbin 24h <prefix>' (and hopefully you see
why this is so).

Second, the '-st', '-e', and associated delta options (just like '-tbin') operate
on all epochs, not just GNSS observation epochs.  Here's where users have run into
misunderstanding: using '+mds' or '+meta' to get the start and final times on
a raw data file, say a Trimble .tgd file, shows only the start and final times of
the GNSS observation epochs, not GNSS ephemerides "Time of Ephemeris" (ToE) and not
meteorological epochs.  Therefore, if you use the start and end times output from
'+mds' or '+meta' to window your data with '-st' and '-e', you run the possibility
of excluding the ephemerides or met data epochs which are outside of the window of
GNSS observation epochs.

Third, if you are inputting RINEX files (GNSS observation, ephemerides, or met),
then you do not need to fully specify the start or end time with '-st' and/or '-e'
all the way to the year.  You need only specify and most precise units and then teqc
uses, where needed, a masking algorithm to fill in the rest.  For example in the case
above let's suppose the input was a RINEX observation file and you wanted to window
the data starting at 02h30m00s.  If so, then you only need to specify '-st 023000'
and teqc gets the year, month, and day from the first epoch of the input RINEX file.
(There's no harm in fully specifying the year, month, day, hour, minute, and second --
you just don't have to specify all if you want to be a bit lazy sometimes.)

Fourth, in general, for '-st and '-e' you'll need to use a four-digit year and two
digits for all other integer units (month to integer second), although the second
value can also include a sub-second portion after a decimal point, '.'.  However,
to make the '-st' or '-e' arguments more readily human readable, you can include
a wide variety of other characters:

T t : , ; / \ + - = _ ~

... meaning that you could specify the start time of today, 2016 Oct 18, with:

-st 2016-10-18T00:00:00
or
-st 2016/10/18_00-00-00
or
-st 20161018000000
or even:
-st 2_+/0-16_1-0:18Tt:0,,0-00:0_0

... although the last example is not too readable by humans.

Inside teqc, all the extra characters are first stripped out and then teqc
parses the string '20161018000000', whether you provide the string that way
or not, so you might as well add some extra characters to make the string more
readable to you and other humans.

A couple of notes:

1) It was pointed out that using '-st' and/or '-e' with sub-second values might
yield a result that not match up with the expected result in email
http://postal.unavco.org/pipermail/teqc/2016/002153.html -- but this was
hopefully fixed on 8 Oct 2016 and will be in the next release:
http://postal.unavco.org/pipermail/teqc/2016/002155.html

2) I've known for a while that when using windowing options like '-st' with '-tbin'
on RINEX observation files that the windowing limits didn't seem to be taking effect.
(There was no problem doing windowing and '-tbin' with raw, BINEX, or RINEX nav or
met files.)  This error was corrected yesterday, 17 Oct 2016 and will be in the
next release.

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




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