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Re: GPS

My office is all of about 250 yards from the building that houses the
GPS program office.  If is staffed by both Air Force and Aerospace
Corporation people.  Being 250 yards away does not quite make me
and insider but I think I'd hear about any major policy shift.

What I do hear is that the system just keeps getting better
A major upgrade to the ground segment is in the works while
continuous small improvements get put into the existing system.
They do keep spare spacecraft on hand and apply a policy of
"launch on anticipated failure".  The system is pretty robust.

There was a lunchtime talk by one of the GPS engineers.  The
topic was General Relatively and GPS.  It seems GPS is one of
the few projects where General Relatively matters.  They deal with
sub-nanosecond per month timing.

I use GPS on my boat.  All last weekend I had no problems getting
4 to 6 satalites with my old Garmin 12 hand held unit.  I'd get
about 35ft horz.. error.

Now a note abut "GPS Time".  Your consumer GPS unit is only going
to be good to about one second.  The display is only updated
once a second and the NEMA data port only transmits once per
second.  The data was good to a nanosecond when transmitted
but is only good to a few "light feet" at ground level.

Tom, are there trees at your location?  wood, plaster, leaves and
people can block the signal.  It is not strong and your antenna
is pretty small.



--- Tom Droege <tdroege2@earthlink.net> wrote:
> Does anyone know the status of GPS these days?  Before Sept 11th, I
> would 
> go out on the porch and within a few minutes I would get 4 or 5
> satellites 
> on my GPS.  Now it takes a long time to get 2, if I get them.  I
> assume 
> that they have turned off a bunch of satellites to keep others from
> using 
> them.  Does anyone know for sure?  I assume that if I get a time it
> is 
> pretty close.  A second or two is all I care about.
> 
> Tom Droege
> 
> 


=====
Chris Albertson 
  Home:   310-376-1029  chrisalbertson90278@yahoo.com
  Cell:   310-990-7550
  Office: 310-336-5189  Christopher.J.Albertson@aero.org

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