[teqc] helpful tip of week 1961

Lou Estey lou at unavco.org
Wed Aug 9 08:00:08 MDT 2017

This week's tip: "less" is usually best

... where by "less" (in bad English), I really mean fewer options, i.e. the minimum set
possible, used in a teqc command.

When users send me all the options they are using with teqc (see 'tip of week 1922'
http://postal.unavco.org/pipermail/teqc/2016/002187.html), usually for translation
or qc of data, sometimes these cases contain options which are not really doing
anything at all or not anything useful or sometimes doing sub-optimal or even actions
contrary to the user's intent.

The 'tip of week 1904', http://postal.unavco.org/pipermail/teqc/2016/002117.html,
covered why you shouldn't use the '-week' option unless you really need to and in
the 'tip of week 1960', http://postal.unavco.org/pipermail/teqc/2016/002xxx.html,
I gave an example of an actual user case where using '-week' with the correct
week value for the desired data created useless RINEX files, whereas leaving the
'-week' option off gave the correct RINEX files.


Let's first review some of the options might really be needed:

o format flags: The use of these was covered in 'tip of week 1899',
http://postal.unavco.org/pipermail/teqc/2016/002096.html.  Basically, if you have
an automated process handling data, it is best to have the format flags for data
for a given site by specified, but usually if you are manually running a teqc command
on a file, then you can probably rely on teqc's auto-identification of the format.
(Exception: whenever you are reading an input stream with teqc -- UNIX/Linux users
will know what I mean -- then you really should include the format flag for the input
data type.)

o '+quiet', '-notice', or '-warn' (see 'tip of week 1911'
http://postal.unavco.org/pipermail/teqc/2016/002134.html: As long as you understand
what you might be missing, sure, use these.

o RINEX header "editing" options: And of course when creating RINEX (or even BINEX),
use the header editing options that start with '-O.' (for RINEX obs headers), '-N.'
(for RINEX nav headers), and '-M.' (for RINEX met headers) all you want -- keeping
in mind you do have to know what you are doing, e.g. see 'tip of week 1931'
http://postal.unavco.org/pipermail/teqc/2017/002208.html for '-O.s'.  There's
also a small set of '+' versions of some of these options with special meaning
which can be used as much as you want, especially for adding new comments
with '+O.c', '+N.c', and '+M.c'.


Now let's review some of the options that should only be used when really needed:

o '-week' option: Use only when absolutely needed on raw data formats, as covered in
'tip of week 1904' and 'tip of week 1960' -- and don't use it when reading RINEX
(because it has no effect when reading RINEX).

o '-max_rx_SVs' option: Following 'tip of week 1912' on this option,
http://postal.unavco.org/pipermail/teqc/2016/002137.html, teqc was modified for
the 2016Nov7 and later releases so that '-max_rx_SVs' is _not_ needed at all for
the following formats (all of which include a CRC or checksum for each record or
     o BINEX
     o Ashtech MBEN stream, R-file, and U-file
     o CMC binary
     o Javad JPS
     o Leica LB2 and MDB
     o Motorola Oncore
     o NavCom SF 2050
     o Rockwell Zodiac
     o Septentrio Binary Format (SBF)
     o Topcon TPS
     o Trimble RT17 and RT27 stream format
     o u-blox UBX
... and the '-max_rx_SVs' option has never had any effect on reading RINEX observation
files.  So when reading RINEX or any of the above formats (with teqc version 2016Nov7
of later), do not include a '-max_rx_SVs' option and expect it to do anything.
But you might need to use this option when reading other formats depending on which
constellations the receiver was set to track.  The most common case we encounter where
'-max_rx_SVs' is probably needed is reading  Trimble .tgd when the Trimble receiver
is set to track most or all GNSS SVs.

o '+rx_clk_off': First, this option is only pertinent when translating.  When the
receiver's computed clock offset value is present in the input data, this option will
output the clock offset value to RINEX obs epochs (where the receiver clock offset value
is an optional field in RINEX obs) and to certain BINEX 0x7f data records, as was discussed
recently at the end of http://postal.unavco.org/pipermail/teqc/2017/002308.html.  In the
past, I've only used this option for outputting the receiver's computed clock offset value
as a test to validate receiver clock resets in the data (checking epoch times and phase
and pseudorange values).  As an operational option, I don't think '+rx_clk_off' is very
useful and certainly should not be depended on.

o '-smtt' option: This will be covered more fully in a future 'tip of the week', but
for now -- unless you really know what this option does -- do not use it and go with
the default '+smtt' (which you don't have to explicitly specify at all since it's
the default).

o '+rds' option = "reverse Doppler sign":  You would only ever want to use this if:
    - you are outputting Doppler observables (which will not be output by default) by
      reading a raw data format and specifying Doppler observables with '-O.obs' option
      or reading a RINEX observation file already containing Doppler observables, _and_
    - the sign of the Doppler observables is wrong without this option (a possible,
      but unlikely, situation).
This is because the sign of Doppler observables in RINEX is specified by a convention,
but this convention is not necessarily what is used in a raw data format.  And sometimes
this little detail of getting the Doppler sign correct gets missed when creating RINEX
from a raw data format.  (Hopefully in all cases of translating raw data to RINEX
with teqc the sign is correct in the resultant RINEX.)

o '+smooth' option = "include smoothing correction to pseudoranges": Some raw data formats
include pseudorange smoothing corrections from the receiver firmware, probably based
on real-time multipath estimates.  Generally, it is considered preferable to not modify
the raw observables, like the pseudoranges, in any way when creating RINEX.  So you
would want to use this option only in very special cases.

o '-rx_ms_adj' option = "do not correct data for millisecond resets": You should
probably never even think about using this option.  (I use it for testing some aspects
of data translation sometimes, when reading formats from receivers that use
millisecond resets as a way of coarsely steering the receiver clock.)

o '-lli' option = "don't show Loss-of-Lock indicator (during qc)": If you are
including this during translation, it does nothing.   This option is meant to
not output the 'L' (loss-of-lock) data symbol in the ASCII time plot during qc.
That's it.

And there are plenty of others.  Generally though, don't use an option just because
you see it in the `teqc +help` output and you think it might be useful.  The options
that are set by default in teqc have been tuned over time and by experience so that
they are almost always the right thing, and the results by overriding them will probably
be sub-optimal.  Put another way, using fewer options is generally the best approach.
And if you have a question about some option that you don't understand, it's also
better to ask about it instead of blindly using it.

Happy teqc-ing!


p.s. Sarah Doelger, one of our NASA GGN engineers here at UNAVCO and who has also been
my unofficial 'tip of the week' proof-reader and editor for a while, is on vacation
this week, so all typos and confusing syntax this week are entirely of my own design.

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

"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', '+all' options - http://postal.unavco.org/pipermail/teqc/2016/002130.html
week 1908: getting RINEX doppler and 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
week 1920: '-M.dec' and '-N.dec' options - http://postal.unavco.org/pipermail/teqc/2016/002163.html
week 1921: combining time filtering options - http://postal.unavco.org/pipermail/teqc/2016/002176.html
week 1922: helping me (or someone else on the list) help you - http://postal.unavco.org/pipermail/teqc/2016/002187.html
week 1923: the "build" line - http://postal.unavco.org/pipermail/teqc/2016/002190.html
week 1924: the qc '-w[idth]' option - http://postal.unavco.org/pipermail/teqc/2016/002193.html
week 1925: qc with explicit time windowing - http://postal.unavco.org/pipermail/teqc/2016/002194.html
week 1926: the '+rx_state' option - http://postal.unavco.org/pipermail/teqc/2016/002200.html
week 1927: the '-O.sum' option - http://postal.unavco.org/pipermail/teqc/2016/002204.html
week 1928: the '+meta' and '+mds' options - http://postal.unavco.org/pipermail/teqc/2016/002206.html
week 1930: more on '-O.sum' - http://postal.unavco.org/pipermail/teqc/2017/002207.html
week 1931: the '-O.s[ystem]' option - http://postal.unavco.org/pipermail/teqc/2017/002208.html
week 1932: leap seconds - http://postal.unavco.org/pipermail/teqc/2017/002215.html
week 1936: what you can (and shouldn't) do in a RINEX obs file - http://postal.unavco.org/pipermail/teqc/2017/002229.html
week 1938: the '+psp' option - http://postal.unavco.org/pipermail/teqc/2017/002231.html
week 1939: the '+diag' option - http://postal.unavco.org/pipermail/teqc/2017/002235.html
week 1951: '-n_<system>' and SV filtering options - http://postal.unavco.org/pipermail/teqc/2017/002277.html
week 1953: more with '+diag' option - http://postal.unavco.org/pipermail/teqc/2017/002287.html
week 1954: using '+diag' output to split raw files - http://postal.unavco.org/pipermail/teqc/2017/002290.html
week 1955: current qc notation - http://postal.unavco.org/pipermail/teqc/2017/002302.html
week 1956: the '+qcq' option - http://postal.unavco.org/pipermail/teqc/2017/002304.html
week 1957: using Trimble formats - http://postal.unavco.org/pipermail/teqc/2017/002305.html
week 1958: ToC != ToE messages - http://postal.unavco.org/pipermail/teqc/2017/002310.html
week 1959: receivers vs. formats - http://postal.unavco.org/pipermail/teqc/2017/002311.html
week 1960: when '-week' is very wrong to use - https://postal.unavco.org/pipermail/teqc/2017/002314.html

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