Re: [fitsbits] Re: Reading floating point FITS files

On Fri 2003-11-14T13:38:04 +1100, Mark Calabretta hath writ:
> Preserve physical data values?  This image may help to clarify matters -
> http://antwrp.gsfc.nasa.gov/apod/ap020920.html

Yes.  I suspect that most original flux data have been eradicated.
In an astronomical image of this sort I can imagine wanting to
compare relative fluxes and change the mapping in ways that
this JPEG does not allow.

> >At best this seems an awful lot like reinventing TIFF in FITS.
> >There should be strong justifications before doing this.
>
> Can TIFF put a celestial coordinate grid on the above image?

Yes, if you admit that geographic coordinates have properties
sufficiently similar to celestial coordinates, via this formalism:
http://www.remotesensing.org/geotiff/geotiff.html

There are a plethora of real estate-related needs for Geographical
Information Systems (GIS) which understand GeoTIFF.  Of the population
which has viewers which can display images with coordinates, I suspect
that more people have GeoTIFF viewers than FITS WCS viewers.

My impression is that the standardization of FITS WCS Paper II is
going to result in FITS viewers that adopt the image manipulation and
overlaying technologies that have long been in GIS.

Nevertheless I would be happy if the folks who are producing pretty
pictures such as this demonstrate that there is a need for the extra
un-ambiguity permitted by FITS coordinates using the formalisms of WCS
Paper II.  Then I'll vote for Mark's notions to go into FITS.

--
Steve Allen          UCO/Lick Observatory       Santa Cruz, CA 95064
[EMAIL PROTECTED]      Voice: +1 831 459 3046     http://www.ucolick.org/~sla
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