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[fitsbits] CDELTn
Well, my question about CDELTn=0 was not related to WCS -- a simple multidimensional hypercube which has several NAXISn set to 1 -- a current practice in FITS. And I'm surprised by Phil's remark: Regardless of the value of NAXISn, computing the coordinate value at a pixel would involve dividing by CDELTn. For example: CRVALn + (1 - CRPIXn) / CDELTn. So it's not as harmless as it may seem. .... I always understood that the coordinate value is CRVALn + (i-CRPIXn)*CDELTn which simply means that the value of the coordinate along this axis is constant and equal to CRVALn, which seems to me perfectly correct (a 1-point dimension is by definition a constant). The formula is not reversible, but it does not be, as far as I know. --Francois ================================================== ============================== Francois Ochsenbein ------ Observatoire Astronomique de Strasbourg 11, rue de l'Universite F-67000 STRASBOURG Phone: +33-(0)390 24 24 29 Email: (France) Fax: +33-(0)390 24 24 32 ================================================== ============================== |
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