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TPV_EVAL

TPV_EVAL

Name


    TPV_EVAL

Purpose


    Compute distorted coordinates given TPV (Tangent + PV_ polynomial)
    coefficients.

Explanation


    See http://fits.gsfc.nasa.gov/registry/tpvwcs.html for the TPV convention
 
    This distortion convention is used by the SCAMP software
    ( http://www.astromatic.net/software/scamp ) though SCAMP does not
    include the '-TPV' in the CTYPE keyword.
 
    The coefficients are passed via common block. This is because this
    routine is called by the intrinisc BROYDEN() function in AD2XY, and
    common blocks are the only way to pass parameters to the user supplied
    function in BROYDEN().

Calling Sequence


    res = TPV_EVAL(xy)

Inputs


    xy - 2 elements vector giving the undistorted X,Y position

Outputs


    res - 2 element vector giving the distorted position

Common Blocks


      common broyden_coeff,pv1,ycoeff
      pv1, YCOEFF are both vectors giving the TPV coefficients

Revision History


    Written W. Landsman Dec 2013
    Correct several typos for 4th power terms M. Sullivan Mar 2014



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