Re: WAAS satellite ( INMARSAT 3-F4 ) moving Feb 1, to 142 degrees West

From: tony dinkel (
Date: Tue Jan 31 2006 - 14:16:51 EST

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    So I guess the question should be...will the ephemeris be continuously 
    updated for the affected PRN as it is moving?  If it is, you could probably 
    watch something change, slowly, assuming you are getting the ephem message 
    with no dropouts.
    Are the Inmarsats used in the actual positional nav solution or are they 
    simply a broadcast conduit for WAAS?
    Also, what is the PRN for the affected SV?
    >The GPS ephemeris is broadcast as part of the GPS data stream. GPS 
    >satellites change orbits, as well as having old satellites retire and new 
    >satellites activated. A GPS receiver with a fixed pre-programmed ephemeris 
    >wouldn't be useful for very long, if at all.
    > wrote:
    >>Kevin said (in part),
    >>"INMARSAT 3-F4 ( 24819) currently at 54 degrees West, is been moved to 142 
    >>degrees West. This satellite is part of the WAAS system, which is used to 
    >>broadcast correction data to GPS users. It will be fun to watch it move 
    >>on, the GPS receiver display.
    >>Kevin and others,
    >>I thought that the position of the satellites as marked on the GPSr 
    >>display was taken from an ephemeris that was programmed into the GPS 
    >>receiver by the maker of the unit. If it is than the WAAS should not move 
    >>in the display. If the data is modified by what the satellite sends out 
    >>then it should.
    >>Anybody know for sure about this?
    >>Tom  Iowa  USA
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