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PcdCen(axis) - Centre coordinates of pincushion/barrel distortion

Description:
This attribute specifies the centre of the pincushion/barrel distortion implemented by a PcdMap. It takes a separate value for each axis of the PcdMap so that, for instance, the settings "PcdCen(1)=345.0,PcdCen(2)=-104.4" specify that the pincushion distortion is centred at positions of 345.0 and -104.4 on axes 1 and 2 respectively. This attribute is set when a PcdMap is created, but may later be modified. If the attribute is cleared, the default value for both axes is zero.
Type:
Floating point.
Class Applicability:
PcdMap
All PcdMaps have this attribute.
Notes:
  • If no axis is specified, (e.g. "PcdCen" instead of "PcdCen(2)"), then a "set" or "clear" operation will affect the attribute value of both axes, while a "get" or "test" operation will use just the PcdCen(1) value.


next up previous 264
Next: Permute - Permute axis order?
Up: AST Attribute Descriptions
Previous: PVi_m - FITS-WCS projection parameters

AST A Library for Handling World Coordinate Systems in Astronomy
Starlink User Note 211
R.F. Warren-Smith & D.S. Berry
24th May 2011
E-mail:ussc@star.rl.ac.uk

Copyright (C) 2009 Science \& Technology Facilities Council