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B.8.2 Examples

Here are some examples of pixsample:

stilts pixsample in=szdata.fits pixdata=wmap_ilc_7yr_v4.fits
                 lat=GAL_LAT lon=GAL_LON pcmd='keepcols TEMPERATURE'
                 out=szdata_cmb.fits
Samples from a HEALPix file containing WMAP data are added to an input file szdata.fits, giving an output file szdata_cmb.fits which is the same but with an additional column TEMPERATURE. The sampling is done using the default statistical mode point, which just takes a point sample at the input position. The HEALPix file must have its pixels ordered using galactic coordinates, since that is the coordinate system available from the input table.

The pixdata file used here can be found (at time of writing) at http://lambda.gsfc.nasa.gov/data/map/dr4/dfp/ilc/wmap_ilc_7yr_v4.fits (24 Mbyte).

stilts pixsample in=messier.xml pixdata=lambda_sfd_ebv.fits
                 stat=mean radius=5./60.
                 insys=icrs pixsys=galactic lon=RA2000 lat=DEC2000
Samples data from a HEALPix table, averaging over a sampling radius of 5 arcmin. The coordinates in the input table are only available as ICRS (RA,Dec) coordinates, and the arrangement of the HEALPix pixels in the pixel data file uses galactic coordinates (you can only determine this by looking at the FITS headers or documentation of that file), so it is necessary to use the insys and pixsys parameters for conversion.

The pixdata file used here can be found (at time of writing) at http://lambda.gsfc.nasa.gov/data/foregrounds/SFD/lambda_sfd_ebv.fits (25 Mbyte).


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Up: pixsample: Samples from a HEALPix pixel data file
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STILTS - Starlink Tables Infrastructure Library Tool Set
Starlink User Note256
STILTS web page: http://www.starlink.ac.uk/stilts/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@jiscmail.ac.uk