Hi Bob:
The ultimate is a carrier phase GPS Timing receiver. The early work was
done using Ashtech Z12 models that have a provision for an external 10
MHz oscillator. I have a feeling that the units you're talking about
are a refinement of this approach.
The new L5 frequency of GPS, intended for FAA use, will allow for
civilian two frequency ionosphere corrections in a more straight forward
way than the existing methods (squaring, Ashtech) of using L2 without
knowing the P(Y) crypto keys.
http://www.prc68.com/I/DAGR.shtml#GPSs
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
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