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    Re: GPS Accuracy Now.
    From: Rodney Myrvaagnes
    Date: 2000 May 03, 9:12 AM

    Attitude determination is not speculation on Rick's part.
    It has been used in aerial photomapping planes for  years.
    In production it would be cheaper than any mechanical gyro
    as well as more accurate. The algorithms are not at all
    exotic, or even computationally difficult.
    
    The FAA has been landing a test 727 automatically for a
    couple of years, trying out various schemes. Among these is
    the use of a pseudolite embedded in the runway, as well as
    ground clearance radar.
    
    A pseudolite is a GPS transmitter, like those in the
    satellites, but fixed to the earth. In the runway, it locks
    the gps solution to the actual piece of ground of greatest
    interest.
    
    
    On Wed, 3 May 2000 10:36:05 -0400, Roger M. Derby wrote:
    
    >What a fascinating speculation.  While your scheme of deriving attitude is
    >certainly feasible, you can, with many nines probability, bet that any
    >aircraft you see will be deriving its attitude information with gyroscopes
    >or Mark I eyeball.  The gyros are laser based for the exotics and mechanical
    >for we, the economically challenged.  (Wouldn't your system need an
    >initialization and integration to detect inverted flight?)  Actually, I
    >believe the use of lasers is limited to the navigational systems and that
    >the cockpit displays and autopilot systems are driven by mechanical gyros in
    >most of the "exotics".  Under mechanical I'm lumping the spinning weight,
    >the vibrating reed, and the air puff systems.  Incidently, aircraft bend
    >more than a few millimeters, so you'd need a rather exotic algorithm to
    >compare nose/tail measurements and or wing tip inputs.  In some aircraft the
    >deflection is measured in feet.
    
    
    
    Rodney Myrvaagnes                   J36 Gjoa
    Senior Editor           Electronic Products
    etaoin shrdlu
    

       
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