[teqc] helpful tip of week 2032

Lou Estey lou at unavco.org
Wed Dec 19 08:23:39 MST 2018

This week's tip: reasons 1-6 that navigation messages might be discarded

The GNSS broadcast navigation messages are one of the pillars that make these systems possible --
the navigation messages being the transmitted digital information sent by the GNSS satellites
themselves about where each one will be (their ephemerides), their SV clock corrections, and
so on. Therefore, managing broadcast navigation messages is important, and sometimes that means
eliminating, ignoring, or skipping irrelevant or problematic or replaced navigation messages.
This tip and the next tries to cover all the reasons when using teqc that GNSS navigation messages
arediscarded in various contexts.

1) SV filtering eliminates corresponding navigation messages. SV filtering was covered
in tip of week 1951, https://postal.unavco.org/pipermail/teqc/2017/002277.html.
If you are filtering out an entire constellation, then all navigation messages
for that constellation are discarded. Or if you are filtering out one or more specific
SVs in a constellation, then all navigation messages for those SVs are discarded.

2) If translating raw data and outputting RINEX 2.xx, there is default filtering for Beidou,
QZSS, and IRNSS -- because these were never officially included in RINEX 2.xx. Therefore,
in order to get Beidou, QZSS, and/or IRNSS navigation messages output as extended RINEX 2.xx
as one or more of the arguments with the '+nav' option, you must also include the '+extend'
option. The '+extend' option was mentioned for this context in
tip of week 1951, https://ls.unavco.org/pipermail/teqc/2017/002277.html and in
tip of week 1955, https://ls.unavco.org/pipermail/teqc/2017/002302.html.

Note: You do not need the '+extend' if both reading and outputting Beidou, QZSS, or IRNSS
RINEX 2.xx, say for the purpose of SV filtering, because teqc assumes you know what you
are doing.

3) Time windowing can filter out ephemerides. You may want to review tip of week 2028
https://postal.unavco.org/pipermail/teqc/2018/002578.html. When using '-tbin' on nav messages,
the time-binning exactly uses the ToC/ToE epochs. When not using '-tbin' on nav messages,
as with normal time windowing or no time windowing, there is an extra time margin, which is
discussed next.

4) Navigation messages with ToC/ToE out of range compared to the GNSS observation epochs
are not used. By default teqc discards navigation messages which are more than 140 minutes
before the first GNSS observation. If desired, this time can be altered by changing the value
with the '-ToE_dt' option, e.g. from `teqc +help`:

-ToE_dt # ToE lookback time in minutes from first observation epoch (default # = 140 minutes = 2h20m)

(This option has been around since early 2009 -- to eliminate old ephemerides that the
receiver might output -- but the default time value has changed since then.)

5) A navigation message where a key value is equal to zero is eliminated. For example,
for any navigation message based on Keplerian elements (GPS, Galileo, Beidou, QZSS, IRNSS),
the square root of the semi-major axis, a, of the orbit is a value that is broadcast, and
obviously any navigation message is useless if the sqrt(a) = 0. There is no option to
override this behaviour.

6) A navigation message with "time of clock" (ToC) not equal to the "time of ephemeris" (ToE)
is discarded. This situation was discussed in tip of week 1958,
For the few cases (so far) of valid ToC != ToC (which is technically allowed for certain
constellations), these valid navigation messages are also discarded. There is no option
to override this behaviour.

Reasons 7-11 will be covered in the next tip of the week.

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

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

Past helpful tips:

week 1894: using teqc config files - https://postal.unavco.org/pipermail/teqc/2016/002067.html
week 1895: qc of high-rate data - https://postal.unavco.org/pipermail/teqc/2016/002071.html
week 1896: UNIX/Linux shells for Windows - https://postal.unavco.org/pipermail/teqc/2016/002072.html
week 1897: '-' vs. '+' teqc options - https://postal.unavco.org/pipermail/teqc/2016/002076.html
week 1898: auto-identification of formats - https://postal.unavco.org/pipermail/teqc/2016/002092.html
week 1899: auto-identification vs. format flags - https://postal.unavco.org/pipermail/teqc/2016/002096.html
week 1900: square brackets in options - https://postal.unavco.org/pipermail/teqc/2016/002105.html
week 1901: using option '+mds' - https://postal.unavco.org/pipermail/teqc/2016/002108.html
week 1902: qc results w/ problematic nav messages - https://postal.unavco.org/pipermail/teqc/2016/002113.html
week 1903: '-no_orb[it]' and '-no_pos[ition]' options - https://postal.unavco.org/pipermail/teqc/2016/002115.html
week 1904: '-week' option - https://postal.unavco.org/pipermail/teqc/2016/002117.html
week 1905: using '+bcf' for XYZ/geodetic conversion - https://postal.unavco.org/pipermail/teqc/2016/002126.html
week 1906: the '+v[erify]' option - https://postal.unavco.org/pipermail/teqc/2016/002128.html
week 1907: '+C2', '+L5', "+L6', '+L7', '+L8', '+all' options - https://postal.unavco.org/pipermail/teqc/2016/002130.html
week 1908: getting RINEX doppler and L2 - https://postal.unavco.org/pipermail/teqc/2016/002131.html
week 1909: using paths w/ file names - https://postal.unavco.org/pipermail/teqc/2016/002132.html
week 1910: the (un)importance of file names - https://postal.unavco.org/pipermail/teqc/2016/002133.html
week 1911: notices, warnings, and errors - https://postal.unavco.org/pipermail/teqc/2016/002134.html
week 1912: the '-max_rx_SVs' option - https://postal.unavco.org/pipermail/teqc/2016/002137.html
week 1913: the end of '++igs' and '+igs' - https://postal.unavco.org/pipermail/teqc/2016/002140.html
week 1914: splicing together RINEX files - https://postal.unavco.org/pipermail/teqc/2016/002144.html
week 1915: using '-O.int' and '-O.dec' - https://postal.unavco.org/pipermail/teqc/2016/002145.html
week 1916: '+doy' option - https://postal.unavco.org/pipermail/teqc/2016/002146.html
week 1917: '-tbin' and '-ast' options - https://postal.unavco.org/pipermail/teqc/2016/002152.html
week 1918: mp12 RMS before/after Oct 2013 - https://postal.unavco.org/pipermail/teqc/2016/002158.html
week 1919: the global windowing options - https://postal.unavco.org/pipermail/teqc/2016/002159.html
week 1920: '-M.dec' and '-N.dec' options - https://postal.unavco.org/pipermail/teqc/2016/002163.html
week 1921: combining time filtering options - https://postal.unavco.org/pipermail/teqc/2016/002176.html
week 1922: helping me (or someone else on the list) help you - https://postal.unavco.org/pipermail/teqc/2016/002187.html
week 1923: the "build" line - https://postal.unavco.org/pipermail/teqc/2016/002190.html
week 1924: the qc '-w[idth]' option - https://postal.unavco.org/pipermail/teqc/2016/002193.html
week 1925: qc with explicit time windowing - https://postal.unavco.org/pipermail/teqc/2016/002194.html
week 1926: the '+rx_state' option - https://postal.unavco.org/pipermail/teqc/2016/002200.html
week 1927: the '-O.sum' option - https://postal.unavco.org/pipermail/teqc/2016/002204.html
week 1928: the '+meta' and '+mds' options - https://postal.unavco.org/pipermail/teqc/2016/002206.html
week 1930: more on '-O.sum' - https://postal.unavco.org/pipermail/teqc/2017/002207.html
week 1931: the '-O.s[ystem]' option - https://postal.unavco.org/pipermail/teqc/2017/002208.html
week 1932: leap seconds - https://postal.unavco.org/pipermail/teqc/2017/002215.html
week 1936: what you can (and shouldn't) do in a RINEX obs file - https://postal.unavco.org/pipermail/teqc/2017/002229.html
week 1938: the '+psp' option - https://postal.unavco.org/pipermail/teqc/2017/002231.html
week 1939: the '+diag' option - https://postal.unavco.org/pipermail/teqc/2017/002235.html
week 1951: '-n_<system>' and SV filtering options - https://postal.unavco.org/pipermail/teqc/2017/002277.html
week 1953: more with '+diag' option - https://postal.unavco.org/pipermail/teqc/2017/002287.html
week 1954: using '+diag' output to split raw files - https://postal.unavco.org/pipermail/teqc/2017/002290.html
week 1955: current qc notation - https://postal.unavco.org/pipermail/teqc/2017/002302.html
week 1956: the '+qcq' option - https://postal.unavco.org/pipermail/teqc/2017/002304.html
week 1957: using Trimble formats - https://postal.unavco.org/pipermail/teqc/2017/002305.html
week 1958: ToC != ToE messages - https://postal.unavco.org/pipermail/teqc/2017/002310.html
week 1959: receivers vs. formats - https://postal.unavco.org/pipermail/teqc/2017/002311.html
week 1960: when the '-week' option is very wrong to use - https://postal.unavco.org/pipermail/teqc/2017/002314.html
week 1961: "less" is usually best - https://postal.unavco.org/pipermail/teqc/2017/002315.html
week 1962: using GPS L2C with teqc - https://postal.unavco.org/pipermail/teqc/2017/002316.html
week 1964: the '+eds' options - https://postal.unavco.org/pipermail/teqc/2017/002317.html
week 1965: handling RINEX comment lines - https://postal.unavco.org/pipermail/teqc/2017/002324.html
week 1966: the '+dUTC_p' options - https://postal.unavco.org/pipermail/teqc/2017/002331.html
week 1967: the strange position from '+meta' - https://postal.unavco.org/pipermail/teqc/2017/002355.html
week 1972: what shows up as metadata in RINEX headers - https://postal.unavco.org/pipermail/teqc/2017/002362.html
week 1973: GPS L2C navigation messages - https://postal.unavco.org/pipermail/teqc/2017/002363.html
week 1974: the '+ion_p' options - https://postal.unavco.org/pipermail/teqc/2017/002370.html
week 1975: the '+event' options - https://postal.unavco.org/pipermail/teqc/2017/002372.html
week 1976: options '+smtt' (default) vs. '-smtt' - https://postal.unavco.org/pipermail/teqc/2017/002374.html
week 1977: the reported interval with '+meta' for a RINEX obs file - https://postal.unavco.org/pipermail/teqc/2017/002377.html
week 1978: the '-N.dUTC' options - https://postal.unavco.org/pipermail/teqc/2017/002378.html
week 1979: the various qc elevation angles - https://postal.unavco.org/pipermail/teqc/2017/002383.html
week 1980: avoid in RINEX: Transit data - https://postal.unavco.org/pipermail/teqc/2017/002385.html
week 1981: avoid in RINEX: epoch flag = 6 - https://postal.unavco.org/pipermail/teqc/2017/002389.html
week 1982: avoid in RINEX: RCV CLOCK OFFS APPL = 1 - https://postal.unavco.org/pipermail/teqc/2018/002392.html
week 1983: don't count on in RINEX: receiver clock offset per epoch - https://postal.unavco.org/pipermail/teqc/2018/002393.html
week 1984: requirements for multiple target files/stdin - https://postal.unavco.org/pipermail/teqc/2018/002410.html
week 1985: default output for various input - https://postal.unavco.org/pipermail/teqc/2018/002412.html
week 1986: the '+latency' options - https://postal.unavco.org/pipermail/teqc/2018/002419.html
week 1987: the 'O.px and 'O.pg' options - https://postal.unavco.org/pipermail/teqc/2018/002422.html
week 1988: the '+relax' option - https://postal.unavco.org/pipermail/teqc/2018/002423.html
week 1992: the '+x_tilt' options - https://postal.unavco.org/pipermail/teqc/2018/002452.html
week 1993: GLONASS: slot and freq. chnl. numbers - https://postal.unavco.org/pipermail/teqc/2018/002453.html
week 1994: GLONASS: slot numbers > 24 - https://postal.unavco.org/pipermail/teqc/2018/002454.html
week 1995: GLONASS: signals - https://postal.unavco.org/pipermail/teqc/2018/002456.html
week 1996: GLONASS: broadcast ephemeris - https://postal.unavco.org/pipermail/teqc/2018/002457.html
week 1997: GLONASS: system time and broadcast time parameters - https://postal.unavco.org/pipermail/teqc/2018/002458.html
week 1998: qc: 'lite' vs. 'full' - https://postal.unavco.org/pipermail/teqc/2018/002470.html
week 1999: qc: the 'full' point-position and the antenna 'height' - https://postal.unavco.org/pipermail/teqc/2018/002474.html
week 2000: qc: what's a "complete observation"? - https://postal.unavco.org/pipermail/teqc/2018/002475.html
week 2001: qc: percentage of actual to expected complete observations - https://postal.unavco.org/pipermail/teqc/2018/002483.html
week 2014: qc: interpreting slips - https://postal.unavco.org/pipermail/teqc/2018/002521.html
week 2015: qc: loss-of-lock - https://postal.unavco.org/pipermail/teqc/2018/002524.html
week 2016: qc: observations per slip - https://postal.unavco.org/pipermail/teqc/2018/002526.html
week 2017: qc: multipath rms - https://postal.unavco.org/pipermail/teqc/2018/002527.html
week 2018: qc: signal-to-noise - https://postal.unavco.org/pipermail/teqc/2018/002532.html
week 2019: qc: the ASCII time plot - https://postal.unavco.org/pipermail/teqc/2018/002534.html
week 2020: qc: little known (but sometimes useful) options - https://postal.unavco.org/pipermail/teqc/2018/002535.html
week 2021: qc: qc full: the '-dn' and '+dn' ASCII time plot lines, part I - https://postal.unavco.org/pipermail/teqc/2018/002544.html
week 2022: qc: qc full: the '-dn' and '+dn' ASCII time plot lines, part II - https://postal.unavco.org/pipermail/teqc/2018/002554.html
week 2023: qc: point-position elevation restrictions - https://postal.unavco.org/pipermail/teqc/2018/002556.html
week 2024: qc: main "filtering" possibilities - https://postal.unavco.org/pipermail/teqc/2018/002557.html
week 2025: qc: expectations for teqc's PP in Solar Cycle 25 - https://postal.unavco.org/pipermail/teqc/2018/002558.html
week 2026: qc: when the antenna is moving (a lot) - https://postal.unavco.org/pipermail/teqc/2018/002564.html
week 2027: qc: direct quality check of raw data - https://postal.unavco.org/pipermail/teqc/2018/002569.html
week 2028: navigation message intervals and using '-tbin' - https://ls.unavco.org/pipermail/teqc/2018/002578.html
week 2029: the '-ns' and '-ne' time windowing options - https://ls.unavco.org/pipermail/teqc/2018/002579.html
week 2030: "no routine" messages in stderr - https://ls.unavco.org/pipermail/teqc/2018/002580.html
week 2031: why zero-length files that are created are left in place - https://postal.unavco.org/pipermail/teqc/2018/002581.html

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