- 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
Corrected 4th order terms once again and
added 5th,6th and 7th order terms Arjun Dey Sep 3, 2015