[teqc] helpful tip of week 1911

Lou Estey lou at unavco.org
Wed Aug 24 08:57:28 MDT 2016


This week's tip:  Notices, and warnings, and errors!  Oh, my!

(Apologies to L. Frank Baum, Noel Langley, Florence Ryerson, Edgar Allan Woolf,
and Judy Garland.)

Perhaps the most disconcerting output from teqc for new users are the messages
labeled "Notice" or "Warning" -- which are often misinterpreted as portents for
the end of the universe.  (The messages labeled as an "Error" new user tend to
understand as an actual error.)

For example, a common notice during translation of a raw data file might be:

! Notice ! NAVSTAR GPS SV G01 in 'my_file': ToC 2016 Jul  1 18:00:00.000 not in 2016 Jul  6 00:00:00.000 to 6075 Dec 31 23:59:59.999 by +/- 
140 min

Is this anything to worry about?  A problematic navigation message?  No, but
this message will be skipped because the date of applicability of the navigation
message (18:00 1 July 2016) is too far away from the data epochs (which, here,
start at 00:00 6 July 2016).  Teqc is tuned to only translate and output navigation
messages which are "close by" the epochs of observation -- by default the actual
epochs of observation, or controlled by time windowing (e.g. using '-st' or '-tbin')
(If the '-week #' option with correct GPS week for the start of data is not being
used, this assumes that teqc has determined the date of the data epochs correctly,
which usually means getting the GPS week right for the start of the data; see
tip of week 1904 for background.)  The time allowance for "close by" is controlled
by the '-ToE_dt #' option which has a default value of # = 140 minutes.  Notice
(pun intended) that the above "Notice" is telling you about a navigation message
that is significantly before the observation data starts and typically you do not
want "old" navigation messages when dealing with "current" data. (If for some
crazy reason you really do want all those old navigation messages, then use the
'-ToE_dt #' option to increase the time allowance around your observation data
to, say, a week with '-ToE_dt 10080'.)

And here's another interesting set of "Notice" messages:

[4496] teqc +mds test.m00
! Notice ! Leica MDB record 104: unknown Leica receiver type= 0
! Notice ! Leica MDB 130: survey starts @ 2016 Aug 23 06:34:45.040 GPS time
! Notice ! Leica MDB record 108: unknown Leica antenna type= 77
! Notice ! ignoring potentially old GPS week in Leica ephemeris record = 1908
! Notice ! ignoring potentially old GPS week in Leica ephemeris record = 1899
! Notice ! ignoring potentially old GPS week in Leica ephemeris record = 1908
! Notice ! Leica MDB 130:   survey ends @ 2016 Aug 23 08:19:41.370 GPS time
2016-08-23 06:34:45  2016-08-23 08:19:30    211452  test.m00

So, a "Notice" from teqc is not a lion to worry about.  It is merely letting you
know something that you are not otherwise going to get to know about or let you
know what it is doing and, once you understand all the ground rules, what it is
doing is probably a good idea as well.  And if you do not want to see any "Notice"
messages at all, use the '-notice' option.  (Here, '-' turns this boolean option
off; see tip of week 1897.)

Now, what about a "Warning"?  Just like in life, a warning is something you should
probably pay a little more attention to, because there is a certain element of risk
involved by ignoring it completely.  Of course, you ignore warnings in real life
all the time, like that speed limit sign on a corner telling you to only go 55 kph
(35 mph) -- and of course you go whipping around the corner at 80 kph ...
(And don't tell me you don't do this, because I know you do.)

So, a "Warning" from teqc may or may not be a tiger lurking in the brush.  This
message is letting you know something where there's a certain risk by ignoring it.
And if you do not want to see any "Warning" messages, use the '-warn[ing]' option
(this being the teqc equivalent to "Damn the torpedoes.  Full speed ahead!").

If you don't want to any "Notice" or "Warning" messages, you can use the '+quiet'
option which is exactly equivalent to '-notice -warn'.  Here at UNAVCO we use the
'+quiet' option for all our automatic teqc commands since we are trying to minimize
unnecessary messages in our data processing logs.   But we also have other pieces
in place to detect certain problems, such as data that might have been translated
with the wrong GPS week.  The good news for outside teqc users like you is that
"Notice" and "Warning" messages have been tuned over the years so that using
'+quiet' to not see any of these is, in the vast majority of cases, reasonably safe,
although you should have other mechanisms in place to check for potential data
integrity problems (along the lines of what we do).

Now, what about an "Error"?  This is more serious -- a 700-kg polar or Kodiak bear
breathing down your neck that wants you for its lunch.  There is no option to block
seeing "Error" messages.  You need to pay attention to these and take action when
spotted.

There is also a small special subset of "? Error ?" messages.  This might be a real
error problem, or it might be false alarm.  You need to take a look and decide.  One
of these is where teqc thinks if has the initial GPS week wrong, for example:

[4497] teqc +quiet +mds problem_file
? Error ? translation may have started with GPS week 1908 rather than 1911
	(try using '-week 1911' option)

In recent years, the most common "? Error ?" situation has to do with the possible
number of SVs being tracked in a epoch, e.g.:

[4498] teqc +quiet my_file > /dev/null
? Error ? 'my_file' rejection due to SV count @ 2016 Jun 14 15:03:00.000 appears wrong: total= 30 max= 22 (use option '-max_rx_SVs 30'?)
? Error ? 'my_file' rejection due to SV count @ 2016 Jun 14 15:03:03.000 appears wrong: total= 31 max= 22 (use option '-max_rx_SVs 31'?)
? Error ? 'my_file' rejection due to SV count @ 2016 Jun 14 15:03:28.000 appears wrong: total= 32 max= 22 (use option '-max_rx_SVs 32'?)

... and here, nowadays, you almost always will have to apply the last suggested
'-max_rx_SVs' setting to get a complete result from teqc.

But more about '-max_rx_SVs' next week.

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



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