[teqc] helpful tip of week 1915

Lou Estey lou at unavco.org
Wed Sep 21 09:51:43 MDT 2016

This week's tip: using options '-O.int' and '-O.dec'

The main use of the '-O.int' option is to specify your intent to have a correct
value, in seconds, for the sampling interval in the optional RINEX observation
header line labeled 'INTERVAL'.  You can use this to correct a wrong value or
insert the INTERVAL line into a file that does not have one.

The use of '-O.dec' is for decimation of the observations to some other interval.
So if the input sampling is, say, 1 second and you want to decimate this to
15-second intervals, use '-O.dec 15'.  If you are using '-O.dec', then the
value specified is what will be written the 'INTERVAL' header line in the RINEX
observation file if RINEX is what you are outputting.

Now, with decimation, an odd thing occurs in the code when the interval is less
than 1 second: you might need to specify what the input interval really is.  Let's
say the input data has 0.1 second intervals and you want to decimate this to 1 second
intervals.  Yes, you will need to use '-O.dec 1'.  However, if you only do this,
the epochs that you end up with might not be what you want.  This is because for
an input interval less than 1 second, to be on the safe side, you should also
include the input interval using the '-O.int' option.  So for the case mentioned
here you should use '-O.dec 1 -O.int 0.1' (or '-O.int 0.1 -O.dec 1', because the
order of the two options does not matter).  You can also include the input interval
with 'O.int' when decimating data where the input interval is 1 second or greater;
it should make no difference in the result.

There is also an undocumented "offset" option with the '-O.dec' option: you can
include an offset to the normal decimated interval.  Let's reconsider that
0.1 second interval data that you want to decimated to 1 second intervals, but
(for whatever reason) you want the epochs that are 0.2 seconds after each second
(= 0.8 seconds before each second), then use '-O.dec 1:0.2 -O.int 0.1' or
'-O.dec 1:-0.8 -O.int 0.1'.

Keep in mind that you don't have to be outputting RINEX observation files to decimate.
For example, you might want to decimate high-rate data during qc; then use '-O.dec'
(and '-O.int' if the input interval < 1 second) along with '+qc' and whatever other
qc options you want.

Happy teqc-ing!


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

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