[teqc] Different times in rinex files if combined than if separate

Lou Estey lou at unavco.org
Thu Aug 3 13:47:21 MDT 2006


Jack,

Another person on the list pointed out that you were probably asking
about the date (yr-mon-day) and not the time (hr-min-sec) on the final
RINEX file, since the raw data showed:

2004-02-07
2004-02-07
2004-02-08

and the RINEX started on the 7th, but shows the end to be on the 15th.
(My bad. Sorry, a case of me focusing on describing moss on the trees instead
of noticing the forest burning down.)

Anyway, _that_ part of what teqc did is wrong.  Obviously, this is related
to the transition of the 7th to the 8th in Feb 2004 being a week rollover,
and teqc switched to a week later than it should have.

Two questions:

Do you get get the epochs for the 8th of the 3rd .dat file incorrectly being
translated as being on the 15th if you use "+smtt" during the translation?

What version of teqc are you using?  (`teqc +id`)  If you're not using the
latest (20 July 2006), could you get the latest at
http://facility.unavco.org/software/teqc/teqc.html#executables
and try it and see if it shows the same problem?

cheers,
--lou

> Jack,
> 
> The short answer is: that's what should happen!
> 
> The time tags in a RINEX file are in receiver time, synched to GPS time
> at the start (by convention).  Handling of receiver millisecond resets,
> which are typical e.g. in Trimble and Ashtech receivers, can be handled
> in one of two ways:
> 
> a) ms jumps in time tag, smooth phase and pseudorange (rx time
> not necessarily = GPS time, except at the start by convention)
> or
> b) smooth time tag, ms (equivalent) jumps in phase and pseudorange
> (rx time = GPS time)
> 
> Either style is equally valid under the RINEX specification, though
> many translators in the early days produced only style (a).
> 
> Clockprep, for example, converts RINEX style (a) into RINEX style (b).
> The other way you can control style is with the smtt option of teqc.
> By default, teqc uses "-smtt" == "not smooth time tag", i.e. style (a)
> (-- for all teqc versions up to now and still current, though
> I am probably going to change this soon)  Using "+smtt" gives style (b).
> 
> So, executing `teqc +meta <whatever>.dat` on each Trimble .dat file
> starts off with rx time = GPS time but drifts due to accumulated
> millisecond resets in the file.  If you instead execute
> `teqc +smtt +meta <whatever>.dat`, you would see the end times on
> your files are:
> 
> final date & time:       2004-02-07 12:44:00.000
> final date & time:       2004-02-07 23:59:45.000
> final date & time:       2004-02-08 08:26:30.000
> 
> During a translate on raw data files to RINEX, teqc (-smtt) keeps
> the accumulated millisecond resets intact when moving from one raw
> file to the next, so your style (a) RINEX file has 199 ms resets
> from GPS time resulting in the final receiver time of 08:26:29.801.
> (If teqc didn't do this, there would be huge time, phase, and pseudorange
> jumps at the boundaries of the input .dat files.)
> 
> If, instead, you translate with +smtt -- resulting in style (b) RINEX --
> the final time will be 08:26:30.000 (GPS time == rx time), which matches
> what you'd see above with `teqc +smtt +meta <whatever>.dat` on the
> last .dat file.
> 
> A good question.  Hope this helps!
> 
> 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
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> 
>> Why am I getting different results when running teqc
>>
>> (a) on three files separately to generate three rinex files
>>
>> vs
>>
>> (b) on the three files together to generate one rinex file?
>>
>> I have three .dat files from a Trimble 5700 receiver. teqc +meta tells 
>> me the times are consecutive, with a short break between the first 2:
>>
>> tcsh: teqc +meta JAR1/39320381.dat
>> ! Notice ! GPS week initially set= 1256
>> filename:                JAR1/39320381.dat
>> file format:             Trimble .dat
>> file size (bytes):       41889
>> start date & time:       2004-02-07 12:32:30.000
>> final date & time:       2004-02-07 12:43:59.998
>>
>> tcsh: teqc +meta JAR1/39320382.dat
>> ! Notice ! GPS week initially set= 1256
>> filename:                JAR1/39320382.dat
>> file format:             Trimble .dat
>> file size (bytes):       1719171
>> start date & time:       2004-02-07 12:49:30.000
>> final date & time:       2004-02-07 23:59:44.882
>>
>> tcsh: teqc +meta JAR1/39320390.dat
>> ! Notice ! GPS week in Trimble Record 21/55h = 1256; (default) GPS 
>> week = 1257
>> ! Notice ! GPS week initially set= 1257
>> filename:                JAR1/39320390.dat
>> file format:             Trimble .dat
>> file size (bytes):       1272415
>> start date & time:       2004-02-08 00:00:00.000
>> final date & time:       2004-02-08 08:26:29.921
>> sample interval:         15.0000
>>
>> If I run teqc separately on the three files to generate rinex files, 
>> the times in the rinex files agree with the times above. However, if I 
>> try <to generate a single rinex file, using
>>
>> teqc -O.int 15 -O.at "TRM22020.00+GP" -tr d +obs jar1038a.04o \
>>      JAR1/39320381.dat JAR1/39320382.dat JAR1/39320390.dat
>>
>> the following lines show up in the middle of the file, where the day 
>> changes, and the times from the last file are shifted from 2/8 to 2/14:
>>
>>  04  2  7 23 59 44.8800000  0 12G 6G 2G24G10G29G27G16G 8G13G17G21G26
>>  -54146557.39547 -42177446.79545 -13116597.0694  -13116602.5974
>>       2414.5164
>> :
>> :
>>  04  2 14 23 59 59.8800000  4  1
>> END OF STATIC OBSERVATION                                   COMMENT
>>  04  2 14 23 59 59.8800000  0 12G 6G 2G24G10G29G27G16G 8G13G17G21G26
>>  -54182718.82847 -42205624.56645 -13123478.7334  -13123483.7764
>>       2406.5474
>>
>> The last epoch in the file is
>>  04  2 15  8 26 29.8010000  0  9G14G25G30G 4G 6G20G24G 5G 1
>>
>> Jack Saba


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