[teqc] start/stop times of ashtech MBEN file

Lou Estey lou at unavco.org
Tue Apr 1 20:03:56 MDT 2008

hi Paul,

> When I use the following teqc command on an Ashtech MBEN file:
> teqc +meta -ash s as25_1900_0100_08.047
> Instead of the usual start/stop time output, I get:
> ! Notice ! GPS week in Ashtech SNV record = 1466; (default) GPS week = 1473
> ! Notice ! GPS week initially set= 1473
> week: 1466
> I assume this is related to the following known issue listed at
> http://facility.unavco.org/software/teqc/bugs.html#current

No, not related to that at all.

> and that the receiver was not configured to output PBEN.  But, if this 
> is a true bug instead of a receiver issue, let me know.

Not a bug either.

Because of format issues (which vary from format to format,
and depend exactly on what metadata may be present or absent),
teqc may have to make certain assumptions about the GPS week
at the start of data.  If using either +meta or +mds, _and_ later
information in the file implies a different GPS week at that
point then teqc has assumed up to that point, then the code
terminates with the message "week: ####" going to stdout.
At that point you need to re-run teqc using "-week ####" put
into the command.

Here at UNAVCO for incoming data our data handling code always
checks for a "week: ####" termination during any +meta or +mds
run and, if found, immediately re-runs the same command with
"-week ####" prepended into the option list.

Does this guarantee a correct start/end time?  No, because
there may be nothing in the file to trigger the "week: ####"
termination.  (Example of such a case: Trimble RT17 stream
data with only 0x57 records -- no 0x55 records (GPS navigation
messages) present.  Here you only know the time of the data
in whatever week the data was collected, but there is nothing
to tell you what the GPS week really is.  Not fun when the data
is N years old and you are trying to figure out what the heck
it is.)

However, _if_ teqc terminates with "week: ####" during a +meta
or +mds execution, just blindly follow its advice and re-run with
"-week ####": it has been tuned so that for the cases we routinely
run into it is at least 99.99% correct.

Hope this helps.


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