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On Wed, 12 Jul 2006, David Berry wrote: > On Tue, 11 Jul 2006, Tim Jenness wrote: > >> On Tue, 11 Jul 2006, David Berry wrote: >> >>> Having said I'll take a look at using the NDF scaled array facilities in >>> CONVERT, I'm not sure what's required. In terms of ndf2fits, I guess there >>> is no need for any change since it already creates BSCALE and BZERO >>> keywords with appropriate values. For fits2ndf, I'm presuming what is >>> needed is a new adam parameter indicating if the resulting NDF should be >>> stored in scaled form or not, although this is a bit messy in view of the >>> existence of the FMTCNV parameter. >>> >>> Have I missed anything? >> >> This work all started because we couldn't read one of those big HI >> survey images when it was uncompressed and, although we worked around it >> by allowing the output type to be specified it made sense for disk space >> to leave it alone and just write scaled FITS files to scaled NDFs >> (this only works if the scaled NDF can internally specify what the >> original target type is, otherwise that HI image would still uncompress >> to _DOUBLE and would still not fit in GAIA). > > So are you saying you want some way for applications to be able to get at > the scaled values? At the moment, the changes I have made only provide > access to the unscaled values (that is, the ARY library automatically > converts the stored integers back into the original floating point values > when the array is mapped). I thought this was what we decided at York. > No, I'm not saying that. I was making the case for FITS2NDF to not expand the scaled FITS arrays but to propogate them to scaled NDFs. I thought you were suggesting that FITS2NDF should not be modified whereas I was saying that we started all this work precisely because we wanted to keep FITS files scaled when converting them. (and the trick was making sure we could convince that HI image to expand to _REAL when it was accessed rather than _DOUBLE). Your York recollection is correct. -- Tim Jenness JAC software http://www.jach.hawaii.edu/~timj