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[fitsbits] CDELTn
Francois Ochsenbein wrote:
And on my side I'm perfectly happy with whatever convention for denegerate axes -- I was just troubled by the fact that fv refuses a FITS file having a CDELTi = 0 for these degenerate axes, and was wondering why. I was not able to reproduce this behavior in fv using either the previous 4.4 version, or the new 5.0 version that was just released last week. Which version are you using? Incidentally, the main new feature of fv 5.0 is that it now uses Calabretta's wcslib library to do all the WCS transformations, and thus now supports the full set of possible WCS projections and not just the half a dozen or so classic projections that were previously supported. Even though the current version of fv does not complain if CDELTn = 0 for a degenerate axis, the FITS WCS papers seem pretty clear that this is not allowed. The proposed new FITS Standard document does mention at one point in the text that CDELTn must be non-zero, but this restriction should probably also be stated in the actual definition of the CDELTn keyword. Bill -- __________________________________________________ __________________ Dr. William Pence NASA/GSFC Code 662 HEASARC +1-301-286-4599 (voice) Greenbelt MD 20771 +1-301-286-1684 (fax) |
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