[time-nuts] Better GPS

[Brooke Clarke]

Hi Bob:

Here's an interesting sidebar:
Precision Modeling for Orbit Determination 
<http://www.aero.org/publications/crosslink/summer2002/02_sidebar2.html>
from the web page:
Orbit Determination and Satellite Navigation
http://www.aero.org/publications/crosslink/summer2002/04.html
I didn't know the Moon tides can change the elevation of LA by 40 cm!

Have Fun,

Brooke Clarke
http://www.PRC68.com


Bob Camp wrote:
> Hi
>
> I've been digging around at acc.igs.org. They seem to think that their clock models are good to below 0.05 ns. They compare that to a 2 ns number for the "as broadcast" models. 2 ns is a pretty familiar number if you look at a lot of TBolt plots. All of their data is online and available for download at some point in time past live. The longer you wait the better the data.
>
> They really like the idea of L1/L2 receivers and fancy post processing. They also are after a lot more than just time. I still have not noticed any complete L1/L2 receivers for<  $100, so I can't do their full solution approach. Ionospheric correction seems to be one big thing you loose by going single freq.
>
> There's a pretty good summary of all that at  http://acc.igs.org/UsingIGSProductsVer21.pdf
>
> Since the TBolt sort but not quite of does carrier phase you might be able to use their data to improve things. I doubt that you would get to 50 ps, but even a 2 or 3X improvement would be worthwhile. Even getting it some of the time (midnight?) would still be useful. It would be a log lots of data and compare thing - not that unusual.
>
> Has anybody else dug into any of this?
>
> Is there a secret stash of cheap L1/L2 fixed location receivers out there that I haven't stumbled across?
>
> Can you really win the lottery by picking up the winning ticket off the sidewalk?
>
> Lots of questions....
>
> Bob
>
>
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-- 
Have Fun,

Brooke Clarke
http://www.PRC68.com