[teqc] Re: NetRS L2-tracking and teqc

Lou Estey lou at unavco.org
Mon Dec 8 10:17:12 MST 2008


hi Mike,

> I request a short update on your progress (or plans) converting Trimble 
> NetRS dat files with L2C. Patty Mothes, my volcano colleague in Ecuador, 
> unknowingly turned on L2C tracking at a number of her stations, and I 
> just noticed that teqc rinex files for satellites that transmit L2C have 
> no L2C or P2 observables.

probably didn't use "+C2" or -O.obs w/ C2 in the requested obs list
during the teqc translation

> I requested that Patty change the affected NetRS to Y-code only 
> tracking, which teqc's into the full complement of rinex code (CA and 
> P2) and phase observables.
> 
> Mike
> 
> Michael Lisowski, mlisowski at usgs.gov
> David A. Johnston Cascades Volcano Observatory
> U.S. Geological Survey
> 1300 SE Cardinal Court #100
> Vancouver, WA 98683-9589
> 360 993-8933, FAX 993-8980

This question is of general enough interest that I'm forwarding it
to the teqc list.  (Hope you don't mind.)  The answer is a little
complicated, so bear with me. If I've got anything wrong with the
Trimble parts, someone at Trimble can then correct me.

pre-1.2-0 firmware on NetRS: If you enable L2C tracking, you can
get L2C code pseudorange (== "C2" in RINEX) for those SVs broadcasting
L2C or the usual cross correlation P2 on L2 for those SVs not
broadcasting it -- but not both for the same SV in an epoch.
For this, the .t00 file from the NetRS is converted into
the usual .dat file which contains the usual record 17 and has
what Trimble calls their "RT17" data payload, which only allows
one code pseudorange per carrier frequency.  If you use the
default conversion with teqc, you just get P2 for those SVs not
broadcasting L2C (because C2 is not included yet in the default
GPS observables), so if you want C2 you have to either use the
"+C2" option (which appends C2 to the default observable list),
or explicitly set the desired observables including C2 with the
-O.obs option.  This works with any teqc version from 2007 June 8
or later.

at 1.2-0 (and I presume later) firmware on the NetRS: If you enable
L2C tracking and collect the usual .t00, you can now create two
different types of .dat files.  Let's say you are using (a recent
version of) Trimble's runpkr00 to do the conversion:

`runpkr00 -d` .t00 -> produces a .dat as described above with the RT17
data payload

`runpkr00 -g -d` w/ .t00 -> produces a .tgd file with the data in
record 27 in what Trimble calls their "RT27" data payload (and the
.tgd file is essentially like a .dat file except that record 27 is
substituted for record 17)

Now, the RT27 data payload allows more than code pseudorange per
carrier frequency, so for those GPS SVs broadcasting L2C you can
get both RINEX C2 and P2 in the same epoch.  It took a long time
for us to get a description of this new record 27 from Trimble,
but we finally got it and an alpha version of reading record 27
was added into teqc in November.  This has not been generally
released, but I have sent teqc builds with it to a few people
for testing.

I've also tested the new data structures for RT27 in the Trimble
stream format.  Generally the story is the same as for the .t00
route, except that you either just get the RT27 version with
streaming, or maybe somewhere there's an option that let's you
decide whether you get RT17 or RT27 in the stream.  As far as
using teqc, it's the same: +C2, -O.obs, 2007 June 8 or later
for RT17, and a version from late 2008 Nov for RT27.

Hope this helps.

cheers,
--lou

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Louis H. Estey, Ph.D.              office:  [+001] 303-381-7456
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