[teqc] helpful tip of week 2021

Lou Estey lou at unavco.org
Wed Oct 3 11:14:28 MDT 2018

This week's tip: qc full: the '-dn' and '+dn' ASCII time plot lines, part I

Next up are two lines in the ASCII time plot that were not in the original qc algorithms
that I inherited from the original authors.  These are probably the least understood parts
of the qc for most users, but these two lines are incredibly useful.  But first note that
these two lines can only be generated when doing qc 'full' (and review tip of the week 1998
for qc 'full' vs. qc 'lite': https://postal.unavco.org/pipermail/teqc/2018/002470.html).

 From the last few lines of the first ASCII time plot in last week's tip:

-dn|   ++++++++++++ ++++++ +++++ ++++ ++  ++++++++++++  ++  ++ +++++++++++++|-dn
+dn|                                          1                             |+dn
Pos| ooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo|Pos
Clk|                                                                        |Clk
00:00:00.000                                                        23:59:45.000
2018 Aug 25                                                          2018 Aug 25

I sometimes refer to the '-dn' and '+dn' lines as the "good news" and "bad news" lines,
respectively, where the object is to summarize the "delta n" discrepancy count of
tracking n SVs, where n is the number one would expect could be tracked above the
cutoff mask angle (which is 10 degrees by default; see tip of week 1979 and the '-set_mask'
option to change this; https://postal.unavco.org/pipermail/teqc/2017/002383.html), i.e.
the SVs should be visible, based on the receiver tracking capability and the SV ephemerides
being used.  Keep in mind that each column of the ASCII time plot is usually summarizing
information for multiple epochs.  For example, if you are using the default "width" of
72 characters (see tip of the week 1924 if you want to change this with the '-w' option;
https://postal.unavco.org/pipermail/teqc/2016/002193.html), and looking at 24-hours of
data at 15 second sampling, then each column is representing 80 epochs.  The meanings are:

'-dn' line shows the maximum number of SVs that are not being tracked in _all_ of the epochs in each column,
'+dn' line shows the maximum number of SVs that are not being tracked in _at least one_ epoch in each column.

In any column, the '-dn' value should be less than or equal to the '+dn' value, and if
the qc is such that there is only epoch for each column of the ASCII timeplot, then
the values in the '-dn' and '+dn' lines for each column should be equal (by definition).

You also have to keep in mind that:

- a blank means a delta n discrepancy of zero ('0' could be used, but doing so makes
the '-dn' and '+dn' lines harder to read at a glance),

- delta n discrepancy counts greater than 9 are represented by 'a', 'b', 'c', ... 'o'
(which then are delta n of 10, 11, 12, ... 24),

- '-' means that the delta n discrepancy count is greater than 24, and

- '+' means more than the expected number of SVs is being tracked, again, given the
cutoff mask angle (10 degrees by default), i.e. the discrepancy is now positive
(more than expected), rather than negative (which is really what the numbers 1-9 and
letters a-o are showing).

Let's look at the '-dn' line above: there are a few blanks (delta n is zero and
so the number of SVs being tracked is exactly what is expected), but many more
columns with '+'.  This means the receiver is successfully tracking SVs below
the default of 10 degrees above the horizon.  So let's iterate and re-qc the data
using '-set_mask' with lower angles and look at the '-dn' and '+dn' lines:

+qc -set_mask 9:
-dn|   ++++++++++++ ++++++ +++++ ++++ ++  ++++++++++++  ++  ++ +++ +++++++++|-dn
+dn|                                          1                             |+dn

+qc -set_mask 5:
-dn|   ++++++ +++++ +++ ++ +++++ ++ + ++  ++++ +++++++  ++  ++ ++  +++++++++|-dn
+dn|   1                                     11 1    1    1  1              |+dn

+qc -set_mask 1:
-dn|   +   +  ++  + +++ +     +   +   ++   +++ ++++  +              +      +|-dn
+dn| 121121121 11 12112112 11221 112112   11 2222 11111 111 22112 111111111 |+dn

+qc -set_mask 0:
-dn|                  +                                                     |-dn
+dn| 121122121111 12222123111221 1222121  2113322111111 21112421211111111121|+dn

... which means that the cutoff angle set in the receiver is essentially at zero degrees.
That is, we have used a few qc runs with different '-set_mask' values and looked at
just these two lines to quickly determine the current working cutoff angle of the receiver.

(Note: The '-set_mask' option can take integer or decimal values, the latter if you really
want to split hairs.)

Now let's go back to the last few lines of the last ASCII time plot in last week's tip,
which was for the SGLG site on 6 Aug 2017 when it was having a bad day:

-dn|-----6 ----   + +  11++ +++++1113 112222231-------------  +    ++   ----|-dn
+dn|------------   1  1111111 ++23--3322223434---------------  1 111 -------|+dn
+10|8787666677776665667777666555677777666678788     77888766555556654444    |+10
Pos|K    oo    oooooooooooooooooo    o            K K       o             KK|Pos
Clk|^^^^^^^^^^^^                  ^^          ^^^^^^^^^^^^^^^        ^^^^^^^|Clk
00:51:30.000                                                        23:00:45.000
2017 Aug  6                                                          2017 Aug  6

We can see that there were times when SGLG's receiver was tracking very well --
there are '+' in the '-dn' line and even a few in the '+dn' line -- but the preponderance
of '-' (i.e. 25 or more SVs not tracked that should have been) is a sure sign that
the receiver is definitely not able to track well.  (Is the cause in the receiver, or antenna,
or the cable?  We don't know from this.)  In fact, one simply does not want to see
any '-' in either the '-dn' or the '+dn' lines; it's a bad sign (pun intended).

Part II on the '-dn' or the '+dn' lines next week, so until then ...

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

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