Back To Overview
The P-Code Generator conflicts with IS-GPS-200E
Posted on 03 Jul, 2011 by KaiZhang
Hello, from the latest IS-GPS-200E, GPS adopts several extended P-codes which are exactly the shifted

version of the old 37 P-Codes.For example, the new P3(t-24) code is exactly the P code of satellite 3

delayed by 24 hours. The first 12 chips of these extended codes are given in IS-GPS-200E. I generated these shifted version of

P-Codes by GPSTK to get the extended codes, but some of the first 12 chips are different from the values

specified in IS-GPS-200E.

For example, the first 12 chips(octal) in IS-GPS-200E is 3545, but the generated value(octal) is 7545. It

is interesting that the error only occurs at the first chip and not all extended P-Codes have this

problem.

Does any one know the author of the P-code generator in GPSTK? Does GPSTK have the plan to update its P-

Code Generator for the additional P-Codes? Anyone knows the email of the author of P-Code generator, please let me know and I'd like to discuss it

with him very much.

Add your comments to the Discussion
 

Wow, does that mean I really found a GPS ICD error? I tried to contact the public interface control working group by email but they didn't response. Good to know the result, thank you! KaiZhang 26 Sep 2011 - 08:01

Kai,
The latest code generator is now checked in at the head. At the public interface control working group meeting last week, three projects (including the GPSTk) agreed that some examples in -200E are incorrect and we agreed on the correct examples. Therefore, the GPSTk sequences will still disagree with -200E, but a future version of -200 should be correct.

Brent Renfro
BrentRenfro 19 Sep 2011 - 09:18

Kai,
After some study at this end, it appears that there are both some problems with the code generator and with the documentation in IS-GPS-200. We believe we have fixed the former and the latter are to be discussed at the public ICWG on the IS-GPS-200 later this week. We're holding off on committing our fixes until we reach agreement with the developers.
Brent
BrentRenfro 12 Sep 2011 - 07:29

Hi,Susan, How is the new P-code generator going? I still don't figure out some of the new extended P code. Is there anyone familiar with this issue in your team? I'd like to discuss it with him very much. KaiZhang 10 Sep 2011 - 21:48

Thanks Susan. I'll hold attention to gpstk's latest update. Wish u can solve it as soon as possible! KaiZhang 09 Jul 2011 - 08:53

Hello again Kai Zhang,

After looking into this, it is the case that these results are not surprising. The P-code generator was developed and tested prior to IS-GPS-200 Rev E and there were only 37 PRN codes at the time. This section of the GPSTk has not been updated to comply with Rev E. We will attempt to incorporate the updated definition in the next two months. Thank you for noting this issue, and for your interest in the GPSTk!

Best Regards,

-- Susan Cummins
SusanCummins 07 Jul 2011 - 15:01

Hi Susan:
I download the source code from http://sourceforge.net/projects/gpstk/files/gpstk/1.7/gpstk-1.7.src.tar.gz/download. I extract the P Code related source code and build a visual studio 2005 project. If you give me a email, I can give you the whole project that validates the problem.
KaiZhang 07 Jul 2011 - 02:13

Dear KaiZhang,

Can you let us know which code version you are working from? Is it the precompiled 1.7 version? Or is it the v1.7 source code? Or have you checked out code using subversion, from the code trunk or one of the development branches? Please let us know what you are working from, and what platform you are running on, as we look into this issue. Thank you!!

Best Regards,

-- Susan Cummins
SusanCummins 05 Jul 2011 - 11:05



Topic revision: r9 - 26 Sep 2011, KaiZhang
 

This site is powered by FoswikiCopyright © by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding Foswiki? Send feedback