The GIS users guide

Associated software note is #55, the User Manual.

• If you are a new GIS user please visit the 'First steps' link in the left hand side menu
• If you are an experienced GIS user please visit the 'In detail' link in the left hand side menu

Reading GIS data into your IDL session:

1. Via a catalogue

GIS data can be located and loaded into your IDL session using xcat. The routine can also be used for displaying spectra.

IDL> xcat, qlds

Then under the Read & View FITS File tab select the Read and Exit with QL data structure? to load a quick look data structure into the IDL session.

The quick look data structure is the standard format of data used by the CDS software. It contains the spectral data, some wavelength calibration information, ancillary information about spacecraft pointing, and much more in a hierarchal structure.

2. Loading files from a personal directory (eg. s4384r00.fits)

IDL> qlds = readcdsfits('s4384r00')

A quick look at the data can be done through the cds_snapshot routine

IDL> cds_snapshot, qlds [, /log]

To browse information in the qlds type:

IDL> help, qlds, /str

or

IDL> help, qlds.header, /str

or

IDL> print, qlds.hdrtext

Now go to the GIS First Steps page