Malcolm,
> CVS commits in period 30 January 2006, 0:00 to 31 January 2006, 0:00
> libraries/kaplibs/kpg/kpg1_wcfax.f
A couple of points:
1) Since presumably the NDF may become large, using the full Mapping to
transform every single pixel position could be very expensive. I would
consider using AST_LINEARAPPROX to test if the Mapping is linear (which
presumably it usually will be), and then use the returned linear
approximation if it is, falling back to the full-blown astTran approach if
it is not.
2) Beware that the method of sandwiching the base->current Mapping between
a pair of PermMaps can produce unpleasant effects if the selected
current Frame axis is not independent of the other axes. The first PermMap
will feed bad values into the non-selected base Frame axes and these can
propagate to the selected output axis if the selected output axis depends
on any of the unselected base Frame axes. The obvious case is if you
select (say) an RA axis - since the Dec is unspecified the RA will also
be unspecified (bad). Using AST_LINEARAPPROX will get round this if
the patch of sky is sufficiently far from the poles to make the RA and Dec
independent. The kpg1_astrm.f function takes another approach.
David
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