[teqc] Re: [gpstech] differential code bias status of receivers

Lou Estey lou at unavco.org
Tue Sep 6 09:35:27 MDT 2005


hi Jim,

Jim Ray wrote:
>>Once the work is done, we should ask that this list be maintained
>>at the IGS Central Bureau, perhaps as part of the rcvr_ant.tab file
>>or as a separate listing (as it is here).  (Angie?)
> 
> 
> To a large extent, it seems that your objective is satisfied by the file
> p1c1bias.hist that I have been maintaining for some time.  For a long time
> it was posted at:
>   ftp://igscb.jpl.nasa.gov/igscb/software/cc2noncc/
> However, I was notified that JPL can no longer bear responsibility for such
> information so it is now deposited at:
>   https://goby.nrl.navy.mil/IGStime/cc2noncc/p1c1bias.hist
> 
> The structure of this file contains several block types, of which one is:
> +cc2noncc/rcvr
> ...
> -cc2noncc/rcvr
> 
> Only the two DCB types that are not your type "N" are listed, all others
> being assumed to be "N" type.  I cannot guarantee that the information
> listed is correct, but every effort has been made to try to ensure
> accuracy.
> 
> Do you believe the existing file is no longer adequate?  I am curious how
> this issue arose (anew).

It started with a question from Bob King and Tom Herring as to how to
categorize the Trimble 5800 and NetRS for Gamit processing.  (I suggested
that Bob post the question, but he wanted it to come from "UNAVCO".)
My impression is that Bob and Tom  want a consensus involving input from
the manufacturers (where the manufacturers still exist).  You'll
also note that the Gamit listing includes many receivers not in
p1c1bias.hist.

> But since you raised this matter, I will note again that this topic will
> soon become vastly more complex with the rapid proliferation in new code
> observables.  The new GPS nav message format has provision for the
> inter-signal biases within the expanded GPS signal set, but the IGS has
> not taken up this issue (as far as I know).

Good points, and a good thread for further discussion.

> FYI, my personal plan was to make only one final update to the cc2noncc
> program then release it for private maintenance by users.  Perhaps UNAVCO
> would be interested in taking it over (or building it into teqc?).

Teqc?  Well, maybe.  I'll admit to only being peripherally knowledgeable
about this issue, but as I understand it, cc2noncc does a cross-correlation
to non-cross correlation correction (as needed, depending on receiver) of
C1, P1, and/or P2 -- so that one ends up with true P1 and P2 equivalents.
But the bias is a function of SV, so the bias changes with time.  (Hence, the
GPS PRN bias history in p1c1bias.hist.)  If that's more or less it, then
the older bias history _could_ be written into teqc as an option for creating
RINEX for processing, with a possible option for reading in a new bias
file for a time period not covered by the (proposed) built-in bias history.
The other tricky part, of course, being how to categorize each receiver
as identified from the RINEX header, and hence the topic of this thread.

cheers,
--lou

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