[teqc] helpful tip of week 1931

Lou Estey lou at unavco.org
Fri Jan 13 09:10:29 MST 2017


This week's tip: the '-O.s[ystem]' option

This little-known option is needed to correct, if need be, what is a quaint, but now somewhat annoying,
part of a RINEX observation file.  From https://igscb.jpl.nasa.gov/igscb/data/format/rinex211.txt
Appendix A, the first line of a RINEX observation file must be formatted according to:

  |RINEX VERSION / TYPE| - Format version (2.11)                  | F9.2,11X,  |
  |                    | - File type ('O' for Observation Data)   |   A1,19X,  |
  |                    | - Satellite System: blank or 'G': GPS    |   A1,19X   |
  |                    |                     'R': GLONASS         |            |
  |                    |                     'S': Geostationary   |            |
  |                    |                          signal payload  |            |
  |                    |                     'E': Galileo         |            |
  |                    |                     'M': Mixed           |            |

Therefore if the observations are GPS-only, the first line should be (at a minimum):

      2.11           O                   G                   RINEX VERSION / TYPE

or if GLONASS-only:

      2.11           O                   R                   RINEX VERSION / TYPE

or if SBAS-only:

      2.11           O                   S                   RINEX VERSION / TYPE

or if Galileo-only:

      2.11           O                   E                   RINEX VERSION / TYPE

or if at any epoch in the file there is a mixture of systems, then:

      2.11           O                   M                   RINEX VERSION / TYPE

The '-O.s' option is used to set the value for the satellite system in this line.  Getting this
value always right in a program like teqc -- which is nominally a one-pass filter -- is impossible.
(Because: this value has to be written to the first line of the file, but in the most general case
one doesn't know the final answer until the very last observation epoch in the file.)
So it is basically up to you, the user, to know what you are tracking and/or filtering.

If you are doing GPS-only and you are doing all the data handling from the receiver and
later, you probably don't have to worry about using '-O.s' because 'G' (GPS-only) should
be the default in that case.  (Actually, the same thing should be true if you are doing
GLONASS-only, SBAS-only, Galileo-only, etc. and then teqc should correctly set the system
to be 'R', 'S, or 'E', respectively.)

However, if you doing fancy stuff like collecting full GNSS data, then you'll probably need to use
the '-O.s' option for at least these cases:

- when the first epoch is not a complete representation of what will be tracked in later epochs

- when constellation filtering and creating filtered RINEX observation file(s)

- when splicing RINEX observation files when different constellation systems might have been
tracked for the different files being spliced

For the last case if '-O.s' is not used or the wrong value might be used, teqc will at least
inform you of some potential conflicts, e.g. the first obs file is 'G' but then a later file
is not 'G'.

(Finally, just an aside, I personally wonder whether any modern software really pays much
attention to this field of a RINEX obs file.  But, good or bad, it's there in the spec, so you
might as well try to get it right.)

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
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

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