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    Re: Help with interpretation of deflection from the vertical
    From: dpstephen
    Date: 2003 Mar 19, 08:22 -0700

    Here is the explanation that I have for interpretation of the information
    shown below:
    
    ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
    A positive meridian component of deflection of the vertical (Xi) indicates
    that the astronomic latitude will fall to the north of the corresponding
    geodetic latitude of the point.
    A positive prime-vertical component of deflection of the vertical (Eta)
    indicates that the astronomic longitude will fall to the east of the
    corresponding geodetic longitude of the point.
    The computed Laplace correction (Hor.Laplace) should be ADDED to a
    clockwise astronomic azimuth, to obtain a "near-geodetic" Laplace azimuth.
    Note: the deflection correction is usually negligible, yielding a
    geodetic azimuth.
    Note: in many textbooks, the Laplace correction is shown with the
    opposite sign and is subtracted from astronomic azimuth.
    +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
    
    So it looks like the astronomical location for your location is too far
    south by about 2.72 seconds ( about 300 feet).
    
    Hopefully I am interpreting this correctly.
    
    
    
    ----- Original Message -----
    From: "Fred Hebard" 
    To: 
    Sent: Tuesday, March 18, 2003 8:05 PM
    Subject: Help with interpretation of deflection from the vertical
    
    
    > I downloaded one of the programs from the geodetic survey site
    > referenced by Doug Stephen, and I also ran the online version of
    > Deflec99, but I'm having trouble interpreting the output.
    >
    > Deflec99's output from the interactive version for my location was:
    >
    >                             latitude        longitude      Xi      Eta
    > Hor Lap
    >    Station Name          ddd mm ss.sssss ddd mm ss.sssss arc-sec arc-sec
    > arc-sec
    >   USER LOCATION            36 46 48.00000  80 50 42.00000   -2.72
    > 0.61   -0.45
    >
    >
    > The intd routine, also from the Deflec99 folder, gave an output of:
    >
    >                              latitude        longitude      Xi      Eta
    >   Hor Lap
    >    Station Name          ddd mm ss.sssss ddd mm ss.sssss arc-sec arc-sec
    > arc-sec
    >   Our House                36 46 48.00000  81 50 42.00000   -2.14
    > 0.33   -0.25
    >
    >
    > For comparison the output for a location near Denver, Colorado, gave:
    >
    >                             latitude        longitude      Xi      Eta
    > Hor Lap
    >    Station Name          ddd mm ss.sssss ddd mm ss.sssss arc-sec arc-sec
    > arc-sec
    >   USER LOCATION            40  0  0.00000 105  5  0.00000    2.06
    > 13.22  -11.09
    >
    >
    > The basic question is, what does this mean?  The readme for Deflec99
    > discusses deviations in azimuth, but deviations in altitude are
    > mentioned less frequently.
    >
    > Thanks,
    >
    > Fred
    
    
    

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