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77 lines
2.1 KiB
Fortran
77 lines
2.1 KiB
Fortran
SUBROUTINE sla_PCD (DISCO,X,Y)
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*+
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* - - - -
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* P C D
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* - - - -
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*
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* Apply pincushion/barrel distortion to a tangent-plane [x,y].
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*
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* Given:
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* DISCO d pincushion/barrel distortion coefficient
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* X,Y d tangent-plane coordinates
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*
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* Returned:
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* X,Y d distorted coordinates
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*
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* Notes:
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*
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* 1) The distortion is of the form RP = R*(1 + C*R**2), where R is
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* the radial distance from the tangent point, C is the DISCO
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* argument, and RP is the radial distance in the presence of
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* the distortion.
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*
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* 2) For pincushion distortion, C is +ve; for barrel distortion,
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* C is -ve.
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*
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* 3) For X,Y in units of one projection radius (in the case of
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* a photographic plate, the focal length), the following
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* DISCO values apply:
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*
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* Geometry DISCO
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*
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* astrograph 0.0
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* Schmidt -0.3333
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* AAT PF doublet +147.069
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* AAT PF triplet +178.585
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* AAT f/8 +21.20
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* JKT f/8 +13.32
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*
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* 4) There is a companion routine, sla_UNPCD, which performs the
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* inverse operation.
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*
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* P.T.Wallace Starlink 3 September 2000
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*
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* Copyright (C) 2000 Rutherford Appleton Laboratory
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*
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* License:
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program (see SLA_CONDITIONS); if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place, Suite 330,
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* Boston, MA 02111-1307 USA
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*
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*-
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IMPLICIT NONE
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DOUBLE PRECISION DISCO,X,Y
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DOUBLE PRECISION F
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F=1D0+DISCO*(X*X+Y*Y)
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X=X*F
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Y=Y*F
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END
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