AGES Data gridding using GRIDZILLA


USERS ARE REFERRED TO AUDS DATA GRIDDING INSTRUCTIONS BEFORE PROCEEDING.

To start Gridzilla type:

% gridzilla

First choose the AUDS parameter set.

The GUI has changed slightly since the AUDS webpage was written. You will notice two differences:
The Data filtering section was introduced to deal with massive RFI from Punta Salinas and Remy. It is not necessary to apply these filters to our data, so set the values to include all your data.  IF YOU DO NOT YOU WILL FIND THAT ANY SOURCE ABOVE 50 mJy WILL BE CLIPPED.

Values that seem to be working so far are Tsys range: 0-100000 and Data range: -1:10.


The Search path is used to locate all your LIVEDATA processed SDFITS files. As you can see you can specify multiple paths.

Highlight all the files that you want to grid by click and dragging over the files you want. Pressing CTRL is useful for picking individual files out of sequence.

 Image centre and extent sets the pixel size in the final image. AUDS default sets the y-scale to 5.2 arcmin, so be sure to change this to 1.

FITS spectral type can be set to your choice. I have been gridding up in frequency but you can equally choose to grid up the data in velocity (optical or radio).

Gridding Statistic should be set to WGTMED.

Set the output directory to be /share/ages/drift_files/DATE (where DATE is of the form YYYMMDD). If this directory has not already been created, you must create it before processing. Gridzilla does NOT perform a validity check on the directory name, if it is not there Gridzilla will fail.
gridzilla screenshor


The result of this processing is a single FITS binary file containing a 3-D dataset called a datacube with axes: RA, dec, frequency/velocity. If, while gridding, MOFONGO cannot hold all the data in memory at once, then it produces a number of smaller datacubelets. These cubelets have the same RA and dec ranges, but limited frequency/velocity ranges. When these cubes are concatenated they will produce a single FITS binary file, with the entire frequency/velocity range. There is a special routine that can do this concatenation called build_cube.csh. To run it  change to the directory containing the datacubelets and type:

% build_cube.csh filebasename

(where filebasename is the output filename you chose in Gridzilla without the .fits extension). As well as creating a single FITS file called filebasename.fits, a number of *.mir directories are also created. This is because miriad is used to do the concatenation. These directories can be safely deleted once the final FITS cube is produced.

This webpage is maintained by Robbie Auld. Page last updated on 28/11/2004