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Disco - PcdMap pincushion/barrel distortion coefficient

Description:
This attribute specifies the pincushion/barrel distortion coefficient used by a PcdMap. This coefficient is set when the PcdMap is created, but may later be modified. If the attribute is cleared, its default value is zero, which gives no distortion. For pincushion distortion, the value should be positive. For barrel distortion, it should be negative.

Note that the forward transformation of a PcdMap applies the distortion specified by this attribute and the inverse transformation removes this distortion. If the PcdMap is inverted (e.g. using AST_INVERT), then the forward transformation will remove the distortion and the inverse transformation will apply it. The distortion itself will still be given by the same value of Disco.

Type:
Double precision.

Class Applicability:
PcdMap
All PcdMaps have this attribute.



next up previous
Next: Domain - Coordinate system domain
Up: AST Attribute Descriptions
Previous: Direction(axis) - Display axis in conventional direction?

AST A Library for Handling World Coordinate Systems in Astronomy
Starlink User Note 210
R.F. Warren-Smith & D.S. Berry
30th April 2003
E-mail:ussc@star.rl.ac.uk

Copyright (C) 2003 Central Laboratory of the Research Councils