[teqc] helpful tip of week 2000

Lou Estey lou at unavco.org
Wed May 9 07:40:14 MDT 2018

This week's tip: qc: what's a "complete observation"?

First, a bit of jargon.  In teqc-land (and elsewhere), any individual measurement
of pseudorange, carrier phase, signal-to-noise, or doppler shift of the carrier
phase at any epoch for any SV is referred to an observable.  For example, we might
have the L5 carrier phase observable for GPS PRN 01 at a particular epoch.

The total combination of all observables for an SV at any particular epoch is the
receiver's "observation" of those observables for that SV at that epoch.  And
exactly what the receiver might be "observing" from any particular SV can change
from epoch to epoch, especially at low elevations where things like multipath and
the probability of loss-of-lock on any particular carrier phase are higher.

The original qc of GPS data was aimed at providing a vetting or proofing of the
collected observables for high-precision processing.  Such processing requires
sets of both pseudorange and phase observables on at least two different carrier
frequencies for each SV being tracked at evenly spaced epochs and collected with one
receiver -- which would coincide with the same sets of observables at the same epochs
(to roughly +/-0.5 millisecond) for one or more other receivers (e.g. reference
stations or other).  As an example, let's say these observables would be the
pseudorange and phase on the GPS L1C/A and L2P(Y) signals for high-precision
processing of GPS data.

So a "complete observation" is, for those constellations with multiple signals,
having both the pseudorange and phase observables at two different carrier frequencies
for an SV.  (Having signal-to-noise and/or doppler observables are not necessary
for this definition.)

However, in the current many-signal GNSS arena exactly what these two different
carrier frequencies might be is somewhat problematic and probably subject to
evolution.  And, for SBAS and IRNSS, a "complete observation" only requires
having both the pseudorange and phase observables for one carrier frequency,
L1C/A and L5, respectively.  Thus, currently, in teqc, a "complete observation" is:

- for GPS, GLONASS, Galileo, Beidou, QZSS: pseudorange and phase on frequency "1"
   and pseudorange and phase on at least one other frequency,

- for SBAS: pseudorange and phase on frequency "1" only (i.e. L1C/A only, even
   if the SBAS SV broadcasts L5),

- for IRNSS: pseudorange and phase on frequency "5" only (i.e. L5 only, because the
   receiver-antenna combinations I'm familiar can't track the S-band IRNSS signal),

where in RINEX 2.11:
     | GPS     L1         1575.42     C1,P1       L1         D1         S1       |
     |         L2         1227.60     C2,P2       L2         D2         S2       |
     |         L5         1176.45      C5         L5         D5         S5       |
     |                                                                           |
     | GLONASS G1         1602+k*9/16 C1,P1       L1         D1         S1       |
     |         G2         1246+k*7/16 C2,P2       L2         D2         S2       |
     |                                                                           |
     | Galileo E2-L1-E1   1575.42      C1         L1         D1         S1       |
     |         E5a        1176.45      C5         L5         D5         S5       |
     |         E5b        1207.140     C7         L7         D7         S7       |
     |         E5a+b      1191.795     C8         L8         D8         S8       |
     |         E6         1278.75      C6         L6         D6         S6       |
     |                                                                           |
     | SBAS    L1         1575.42      C1         L1         D1         S1       |
     |         L5         1176.45      C5         L5         D5         S5       |

and in RINEX 2.11 "extended" (discussed in previous emails, e.g. tip of week 1995
     | GPS     L1C        1575.42      C7         L7         D7         S7       |
     |                                                                           |
     | GLONASS G3         1202.025     C7         L7         D7         S7       |
     |                                                                           |
     | Beidou  B1/E2  I/Q 1561.098     C1         L1         D1         S1       |
     |         B2/E5b I/Q 1207.14      C7         L7         D7         S7       |
     |         B2a    I/Q 1176.45      C5         L5         D5         S5       |
     |         B3/E6  I/Q 1268.52      C6         L6         D6         S6       |
     |         B1-2/E1    1589.742     C2         L2         D2         S2       |
     |         B1C        1575.42      C8         L8         D8         S8       |
     |                                                                           |
     | QZSS    L1C/A      1575.42      C1         L1         D1         S1       |
     |         L1C        1575.42      C7         L7         D7         S7       |
     |         L1-SAIF    1575.42      C8         L8         D8         S8       |
     |         L2C        1227.60      C2         L2         D2         S2       |
     |         L5     I/Q 1176.45      C5         L5         D5         S5       |
     |                                                                           |
     | IRNSS   L5     I/Q 1176.45      C5         L5         D5         S5       |

Thus, if the receiver happened to be tracking only GPS L2C and L5, there would be
no complete observations counted for any GPS SV with the current teqc (i.e. tracking
on GPS L1C/A and/or L1P(Y) would also be needed to get any "complete observations").

Hopefully this all makes sense.  Admittedly, a "complete observation" was simpler
to understand in the early GNSS days when there was only GPS and the only GPS signals
where on the L1 and L2 carriers.

And, obviously, if there are any new high-precision processing considerations that
need to be taken into account, I'd be willing to modify the requirements for a
"complete observation" for a constellation.  Just let me know.

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

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