[teqc] "Possible obs > 0.0 deg" is decreasing?

Lou Estey lou at unavco.org
Thu Apr 8 08:02:39 MDT 2010


The following is from Jim Ray, NOAA/NGS.  (Jim and a few others on
the list are hesitant to post an email because e-addresses get stored
on-line by our Mailman list server.  I can't blame them.  The e-addresses
are obfuscated a bit by Mailman, but not enough to prevent harvesting
of e-addresses by sophisticated spambots -- if they can find the teqc
and other lists, which are now a bit hidden (i.e. no direct links from
the UNAVCO web site.)  Me?  I'm doomed already to spam purgatory. :( )


-------- Original Message --------
Subject: Re: [teqc] "Possible obs > 0.0 deg" is decreasing?
Date: Thu, 08 Apr 2010 09:49:20 -0400
From: Jim.Ray
To: teqc <teqc at ls.unavco.org>


I think Lou is correct.  Till 29 Feb 2010 you could observe
up to 32 SVs (including all healthy and unhealthy).  On that
day PRN25 stop broadcasting and it was later moved into a
disposal orbit.  (This SV was never set healthy after it was
turned back on though.)  Despite this, a lot of IGS receivers
continue to report bogus nav messages for PRN25.

Then PRN09, which was scheduled for a maneuver starting on
23 Mar 2010, stopped broadcasting during that time and has
not come back yet.  There has been no public information
about what's going on with this SV.  So I don't know if it
will ever come back or not.  It is 17 years old.  Also, some
IGS receivers continue to report bogus nav messages for PRN09
too.

Meanwhile, PRN01 has not been set healthy since its launch
a year ago and it remains unclear if/when it will ever be
set healthy.  Recently, its nav messages have become sparse
for unknown reasons.

So presently you can track at most 30 SVs but probably only
up to 29 because of PRN01.  Recently there have been steady
NANU events (mostly MX) that remove 1 SV on some days if
your receiver does not track healthy SVs.

I won't try to speculate on where things might be headed
from here.

--Jim



Lou Estey wrote:
>> My GPS receiver is working at "Observation interval : 1.0000 seconds"
>> but the "Possible obs > 0.0 deg" is decreasing,and the raw data size
>> is also
>> decreasing, why?The raw data size jpg is accessories.
>>
>> *************
>> Time of start of window : 2010 Mar 1 00:00:00.000
>> Time of end of window : 2010 Mar 1 23:59:59.000
>> Time line window length : 24.00 hour(s), ticked every 3.0 hour(s)
>> |qc - header| position : 34 m
>> Observation interval : 1.0000 seconds
>> Total satellites w/ obs : 32
>> NAVSTAR GPS SVs w/o OBS :
>> NAVSTAR GPS SVs w/o NAV :
>> Rx tracking capability : 12 SVs
>> Poss. # of obs epochs : 86400
>> Epochs w/ observations : 86400
>> Epochs repeated : 0 (0.00%)
>> Possible obs > 0.0 deg: 980912
>> ---------------------
>> Time of start of window : 2010 Mar 2 00:00:00.000
>> Time of end of window : 2010 Mar 2 23:59:59.000
>> Time line window length : 24.00 hour(s), ticked every 3.0 hour(s)
>> |qc - header| position : 32 m
>> Observation interval : 1.0000 seconds
>> Total satellites w/ obs : 31
>> NAVSTAR GPS SVs w/o OBS : 25
>> NAVSTAR GPS SVs w/o NAV :
>> Rx tracking capability : 12 SVs
>> Poss. # of obs epochs : 86400
>> Epochs w/ observations : 86400
>> Epochs repeated : 0 (0.00%)
>> Possible obs > 0.0 deg: 946938
>> --------------------------
>> Time of start of window : 2010 Mar 23 00:00:00.000
>> Time of end of window : 2010 Mar 23 23:59:59.000
>> Time line window length : 24.00 hour(s), ticked every 3.0 hour(s)
>> |qc - header| position : 28 m
>> Observation interval : 1.0000 seconds
>> Total satellites w/ obs : 31
>> NAVSTAR GPS SVs w/o OBS : 25
>> NAVSTAR GPS SVs w/o NAV : 1
>> Rx tracking capability : 12 SVs
>> Poss. # of obs epochs : 86400
>> Epochs w/ observations : 86400
>> Epochs repeated : 0 (0.00%)
>> Possible obs > 0.0 deg: 915266
>> ---------------------------------
>> Time of start of window : 2010 Mar 24 00:00:00.000
>> Time of end of window : 2010 Mar 24 23:59:59.000
>> Time line window length : 24.00 hour(s), ticked every 3.0 hour(s)
>> |qc - header| position : 32 m
>> Observation interval : 1.0000 seconds
>> Total satellites w/ obs : 31
>> NAVSTAR GPS SVs w/o OBS : 25
>> NAVSTAR GPS SVs w/o NAV : 1
>> Rx tracking capability : 12 SVs
>> Poss. # of obs epochs : 86400
>> Epochs w/ observations : 86400
>> Epochs repeated : 0 (0.00%)
>> Possible obs > 0.0 deg: 915316
>
> Most likely because the visible GPS constellation is changing day by day.
> (Assuming you have all the appropriate GPS nav messages in the input
> file(s) to do the qc.)
>
> 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
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


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