Problems with GPS SVN49/PRN01

Based on the recently mentioned problems with the new GPS satellite PRN01 I
have had a look at it using the data from the IGS network (http://igs.org ).

I have put the results on my BLOG at http://gnss.servolux.nl/gnss_blog.html
so go there to see a detailed look at the problems with this satellite.

In summary the results I obtained show that it is clear that there is a
small problem with the code observations when used simultaneously with the
phase observations. This problem is only at the few meter level and thus not
really important. The cause is most likely an issue with the so called group
delay of the code observations.

What is much more problematic is that the broadcast ephemerides are very
poor. When compared with an orbit determination, like the IGS is doing, the
differences seem to be at the 60 km level!! The reason for this is unclear
at present for "normal" observers like me. So there must be more at hand
then the view meters we see in the code residuals....

I will update my BLOG as soon as I learn more about this problem.

Cheers,
Tim
http://gnss.servolux.nl/gnss_blog.html

wrote:
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The daily observations for PRN01now show a satellite error that is now
consistently less than a meter.

http://gps.afspc.af.mil/gpsoc/performance_reports.aspx

That's approaching the performance of the overall IIR satellite
family. PRN01 recently has been generally outperforming PRN30, an old
satellite which is in a nearly identical orbit.

--- CHAS

HIPAR wrote:

That's a very interesting set of reports.

I'm particularly intrigued by

http://gps.afspc.af.mil/gpsoc/products/uclas_world_pps_aiv.jpg

which shows the maximum position error when using All In View sats:

Pretty much the entire CONUS is in the 4-8 m range, with a small slice
of the eastern seaboard below that, while nearly all of Europe is in the
0-4 m class, i.e. significantly better performance here.

Terje

--
"almost all programming can be viewed as an exercise in caching"

You in Europe are likely reaping the incidental benfits of GETS - GPS
Enhanced Theater Support. 2SOPS, in supporting the ongoing conflicts in
Southwest Asia, schedules the (usually daily) upload of each satellite
shortly before it is about to rise over that area of the world. So, the
satellites in view of SW Asia all have the lowest Age of Data for their
ephemerides. Between GETS and WAGE (Wide Area GPS Enhancement, the typically
encrypted NMCT data in the almanac), a properly equipped PPS receiver can
achieve 1-2 meter accuracy in theater. Since Europe is "close enough" to
SWA, you get fresher ephemeris data as well. Isn't that nice?

-Marty

Be careful in interpreting or applying that graphic. Not only is it only
from a 24 specifically defined period, it is difficult to model "maximum "
error. This graphic is likely some sort of statical calculation rather than
actual measurements and it is unfortunate that exactly how it was derived is
not explained. ( I suspect it is not "maximum" error in the sense that many
would think what those words mean.)