[teqc] Re: teqc Digest, Vol 72, Issue 3

Lou Estey lou at unavco.org
Wed Mar 10 05:34:05 MST 2010


GPS wrote:
> If you are using a old version of TEQC, try to use together with TEQC 
> command the TEQC key -week WWWW where WWWW is the GPS Week that 
> correspond the DAT file. With versions of TEQC  I experienced some wrong 
> translations from DAT to RINEX when I ommit the key -week. My 
> observation files was translated to wrong date time. The receiver was NetRS.
>  
> I suggest you try -week TEQC key
>  
> for example, today, I translate a DAT file using this command
>    
> teqc -tr d -week 1574 site0690.dat > site0690.10o

True enough, on occasion.  The problem is that the .dat data records,
record 17 (i.e. the .dat version of Trimble's RT17 data payload),
do not contain the GPS week information.  (They contain a time
stamp of seconds into the week, but which GPS week??)  So, teqc
has to divine the GPS week information from elsewhere.   The
approximate path is:

* assume GPS week based on OS system time (a reasonable backup if
the data is very current)

* use start time in .mes file (but .mes might be missing, and
the date in this file has been known to be very wrong)

* use GPS week in various other records that might be in the .dat
file (but these records might not be there, or the GPS week value
in one or more of them might be wrong)

* guess at GPS week of data based on time tags of GPS navigation
messages (if these messages are in the .dat file): assume data
is within +/- 0.5 week of the initial nav messages

So, if you don't use -week with a correct value, teqc does it's
best with this imperfect situation -- and usually figures out what
the GPS week is, but this might be well after the first data epochs
with an assumed inaccurate GPS week.  Then you get an error message.

Here's what we do for _all_ .dat files: We first use '+meta' or
'+mds' on each .dat file.  If teqc gets to the point where the initial
GPS week guesstimate for the start of data appears to be wrong, teqc
will terminate with

week: {GPS_week_value}

e.g. the above .dat would have terminated with

week: 1574

If it does terminate that way, re-run with the '-week' option
and the supplied value.  If it doesn't terminate that way, then
teqc almost certainly has the right GPS week.  (There are still
very rare exceptions though ...)

--lou

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Louis H. Estey, Ph.D.              office:  [+001] 303-381-7456
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"If the universe is the answer, what is the question?"
                                                -- Leon Lederman
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