[teqc] problem with GNSS nav time()

Lou Estey lou at unavco.org
Wed Jun 6 09:15:39 MDT 2018


dear Susilo,

Thanks for the sample Leica MDB file for the 2017-196 to 2017-197 (GPS week
1957 to 1958) rollover with Beidou navigation messages.

Nominally, I think everything is correct in the Beidou RINEX nav file, except
for the ToW values, which are all 14 seconds too large -- for all Beidou messages
in the RINEX nav file, regardless of when in a week they occur.  However, this is a
minor point, because Leica formats don't really store the ToW, and I use something
else as a proxy.  In this case, I'm using the record time itself as the proxy,
which is in GPS time, but I forgot to subtract the 14 seconds offset between
GPST and BDT.  This minor detail has been corrected and will be in the next
release.  (And note that the ToW doesn't really have any impact on using the
rest of the navigation message for SV position determination.)

However, for now I'm going to leave in place the flag that results in the notice:

! Notice ! GNSS_nav_time(): case of Leica Beidou nav record for Beidou nav message needs testing for validity during week rollover

(The same flag will result in a similar message for Leica MDB data with Galileo
or QZSS navigation messages and for BINEX with IRNSS navigation messages.)

The reason for leaving the notice in place is that we probably need more than
one case to be tested.

However, I'd like to stress that the majority of translated navigation messages
where you might see this (e.g. Beidou nav from Leica MDB) will be perfectly fine
(aside from the unrelated ToW issue mentioned above for Beidou nav from Leica MDB).
There is only the possibility of a few navigation messages right at a week rollover
that might not be not be translated properly.  But the odds are pretty low because
I'm basing logic for these few cases on what happens in those formats for the
other GNSS nav systems which have been thoroughly tested now at week rollovers.
So as long as the rx firmware is consistent between all GNSS nav that it's handling,
all should be well.

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

"If the universe is the answer, what is the question?"
                                                -- Leon Lederman
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

On 05-Jun-18 01:44 PM, Lou Estey wrote:
> Completely unrelated.  The notice about the GNSS_nav_time() would only be pertinent
> when outputting Beidou RINEX nav, and then only if the Beidou navigation messages
> rolled from one week to the next.  I doubt you are creating those and reading them
> in GAMIT/GLOBK.  (The mentioned case for GNSS_nav_time() -- Beidou navigation messages
> from Leica MDB at week rollover -- is one that I don't have data to test.)
> 
> If you do a `teqc -O.sum . <filename>` on one of the RINEX obs files being created
> by teqc and used in GAMIT/GLOBK, what do you get back?
> 
> --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
> 
> "If the universe is the answer, what is the question?"
>                                                 -- Leon Lederman
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> On 05-Jun-18 01:17 PM, Susilo, ST wrote:
>> Dear All,
>>
>> I have some problem with leica MDB from GS14 when i convert using teqc.
>> there was a notice:
>>
>> ! Notice ! Leica MDB 130: survey starts @ 2017 Jul 10 11:11:17.040 GPS time
>> ! Notice ! GNSS_nav_time(): case of Leica Beidou nav record for Beidou nav message needs testing for validity during week rollover
>> ! Notice ! Leica MDB 130:   survey ends @ 2017 Jul 12 00:31:17.800 GPS time
>>
>> Actually the teqc still produce the rinex observation file. But the problem is when i process the rinex data using GAMIT/GLOBK most of the 
>> observation is rejected.
>> Is there any relation with the teqc notice about GPS_nav_time():
>>
>> Anybody could explain about that?
>>
>> Thank you for your help
>>
>>
>> Best regards,
>>
>>
>> Susilo
>>
>> ===========================================
>>
>> Center for Geodetic Control Network and Geodynamics
>>
>> Geospatial Information Agency
>>
>> former BAKOSURTANAL
>>
>> Jl. Raya Jakarta-Bogor Km. 46 Cibinong - Bogor, INDONESIA
>>
>> Phone/fax: +62-21-8758061
>>
>> email: susilo at big.go.id; susilosarimun at gmail.com



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