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Accessing images of differing formats

GAIA can display and perform analyses on many different data formats. It does this by using the ``on-the-fly'' conversion facilities of the NDF library, which it uses directly. This on-the-fly conversion uses external programs that can convert your data from its current format into an NDF and then back again (if necessary).

The CONVERT (SUN/55) package provides many formats that are useful for astronomers (e.g. FITS, IRAF and old FIGARO formats) and is automatically used by GAIA (unless you have set up your own conversion facilities, see SSN/20 if you think you need to do this). All the formats recognised at any time by GAIA are shown in a menu in the file chooser, so check this to see if your format is available.

FITS files are a special case in that GAIA will read these natively (which gains increased efficiency), however, any external analysis routines (such as those used in the photometry toolbox) will still need to be able to convert these files into NDFs, using the on-the-fly facility, so if you define your own conversion facilities make sure that you include a FITS converter (note these doesn't apply to FITS data cubes, GAIA handles converting these into NDFs for the various toolboxes directly).

To display any of these images in GAIA just type the full disk-file name on the command-line (either when you start GAIA or by using the gaiadisp command), or similarly select the disk-file in the open file window.

To display a FITS file extension image, either open the disk file and choose the extension from the HDU selector window that appears, or add the extension number to the disk-file name:

# gaia mef_file.fits'[2]'
The FITS primary array is number $1$.

A similar mechanism exists for NDFs stored in container files at other than the top-level:

# gaia hdscontainer.ndf_1
In this case any other NDFs stored at the same level in the container file will also be shown in a selector window. NDF slices can also be used:
# gaia hdscontainer.ndf_1'(200:500,100:700)'
This can also be applied to FITS files and other foreign formats, but note that this means that FITS files will now be accessed as foreign, i.e. the FITS files will really be NDFs:
# gaia file.fits'(300:700,300:700)'

next up previous 69
Next: SAMP interoperability
Up: What does it actually do?
Previous: CUPID catalogues and masks

GAIA -- Graphical Astronomy and Image Analysis Tool
Starlink User Note 214
Peter W. Draper,
Norman Gray,
David S. Berry &
Mark Taylor
23rd April 2012

Copyright © 2012 Science and Technology Facilities Council