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

[Lou Estey]

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