[teqc] helpful tip of week 2025

Lou Estey lou at unavco.org
Wed Oct 31 07:29:05 MDT 2018

This week's tip: qc: expectations for teqc's PP in Solar Cycle 25

We are currently nearing the end of Solar Cycle 24 and the beginning of Solar Cycle 25,
and thus near a solar minimum; for example, see
https://www.swpc.noaa.gov/products/solar-cycle-progression and
This year has been a good time to fine-tune teqc's point positioning, given that ICD
ionospheric modeling is not done in teqc due to the sparsity or even total lack of
ionospheric model parameters in most source datasets. The following discussion assumes
a teqc version of at least 2018Mar15 or later.

Here at UNAVCO, a qc full is done on incoming permanent station data whenever the
site provides GNSS ephemerides collected at the site, i.e. the idea is to quality
check not only the GNSS observables, but also the GNSS ephemerides collected at
the site.  This amounts to roughly 1500 - 1700 sites every day with both GNSS
observation data and ephemerides, and usually 24 hours of GNSS observation data
at each site.  Teqc's PP for each site can then be compared to what we have in our
database as the approximate position for that and (after correcting a number of
obvious errors in our database), the current differences (*) can roughly be
described this way:

- There is a mean vertical offset of teqc's PP of roughly +14-16 meters from the
true position (although for a handful of sites this vertical offset is a bit larger).

- After subtracting out this mean vertical offset, the vertical offset distribution
is about twice that of the horizontal offset distribution.

- About 70-80% of teqc's horizontal positions fall within 1.5 meters of the true
horizontal positions.

- After subtracting out the mean vertical offset, about 70-80% of teqc's vertical
positions fall within 3 meters of the true vertical positions.

You can then visualize teqc's PP uncertainty distribution as being centered about
14-16 meters above the true position, with a horizontal 1-sigma of about 1.4 meters,
and a vertical 1-sigma, from the center of the distribution, of about 2.8 meters.
And, again, this is for data near a solar minimum, and using 24 hours of GNSS pseudoranges,
and a fairly complete set of GNSS ephemerides for the pseudoranges being used in the PP.

Now, how might this change during the upcoming Solar Cycle 25?

Assuming Solar Cycle 25 acts approximately like the last Cycle 24, one can use qc
results from Cycle 24 as a proxy to get an estimate.  To that end, teqc PP solutions
for the following periods will be discussed, going back in time:

±2 weeks around 1 Sep 2018 -- close (enough) to the solar minimum at the end of
Solar Cycle 24

±2 weeks around 1 Nov 2015 -- about midway in solar activity between the solar maximum
for Solar Cycle 24 and the solar minimum at the end of Solar Cycle 24

±2 weeks around 1 Feb 2014 -- around the time of the solar maximum for Solar Cycle 24

Ideally, one would use the current teqc to qc data during Solar Cycle 24 and compare
teqc's PP with the sites' actual positions, after adjusting for tectonic movements
at each site.  Well, that's more than I have the time and wherewithal to do, so I've
opted for a one-site estimator.

Enter, stage left, permanent station P197.  P197 is noteworthy for several reasons:

- Its motion in any reference frame is incredibly boring, e.g see Geoff Blewitt's
IGS08 solutions http://geodesy.unr.edu/NGLStationPages/stations/P197.sta
or UNAVCO's GAGE NAM08 solutions

- Its vertical motion is almost zero over 13+ years -- just a bit of seasonal oscillation,
even after a receiver and antenna change in Jan 2015.

- Its vertical survey point position is within a couple of centimeters of being exactly
on the WGS84 reference ellipsoid surface.  (In fact, this is the closest of any GNSS
site that I know of, with the runner-up being RPFB, which has a vertical survey point position
about 8-12 centimeters from the WGS84 reference ellipsoid surface.)

- Its horizontal survey point position changed only by about 2 decimeters since early 2014.

- Yours truly helped install P197 in August 2005.

The all-important last reason aside, these features of P197 mean that for rough comparisons
to teqc's PP we don't have to be too concerned about P197's motion during that last few years,
and that we don't have to worry about P197's ellipsoid height.

First, let's look at differences from teqc's PP from the actual position of P197 for the
±2 weeks around 1 Sept 2018 (close enough to the solar minimum): teqc's vertical offset
varies from +12.7 to +15.3 meters above P197's actual position, and teqc's horizontal
offset varies from 0.5 to 1.3 meters from the actual position.

Next, the offsets for the ±2 weeks around 1 Nov 2015 (about midway between the last solar
maximum and upcoming minimum): teqc's vertical offset varies from +13.2 to +17.3 meters
above the actual position, and teqc's horizontal offset varies from 1.2 to 2.9 meters
from the actual position.

Next, the offsets for the ±2 weeks around 1 Feb 2014 (near the last solar maximum):
teqc's vertical offset varies from +16.9 to +23.1 meters above the actual position,
and teqc's horizontal offset varies from 0.9 to 1.6 meters from the actual position.
There is also quite a bit of day-to-day variability in these offsets.

 From this, again, assuming one has 24-hours of worth of data and ephemerides, my expectations
for teqc's PP during Solar Cycle 25 are that:

1) The vertical offset will increase by up to 10 (and perhaps a few more) meters as the
solar maximum is approached compared to the currently observed vertical offsets.

2) The horizontal offset will increase by a factor of 2-3 compared to the currently observed
horizontal offsets, but typically will be within about 5-6 meters, horizontally, of the
real position.

Happy teqc-ing!

* Again, the currently observed offsets are for the current period of time (summer & fall
of 2018), which is close to the solar minimum between Solar Cycles 24 and 25.


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

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