[daip] AIPS frustration-related issue

[Eric Greisen]

Bob Garwood wrote:
> 1) Does the reweight[2] value refer to the weight in the gridded image - 
> i.e. those cells with a final weight below this value are blanked - or 
> does it refer to the weight assigned to the data when it's loaded in 
> from the external file (i.e. prior to gridding).
> 
> 2) Can someone remind me what the available tools are for looking at the 
> ungridded data values and weights? (plots would be nicer than just 
> tabulated output)

REWEIGHT(2) refers to the sum of the products of the data weights and 
the convolution function weights at each cell scaled by the maximum such 
sum.  Output cells with weights below REWEIGHT(2) * Max_convolved_weight
are blanked.  This is what the help file says.  The input data weights 
are not examined, they are just used.  That is partly an error - it 
should at least be looking for flagged data (weights <= 0) and not 
including them.  Other interferometry tasks allow the user to alter the 
data weights on input (e.g. use sqrt, fourth root, 1, ...)  If these 
options are needed I can fix the code.

The available tools and how one uses them for single-dish work are 
described in chapter 10 of the AIPS Cookbook.  The PostScript of that is 
available at your site as $AIPS_ROOT/TEXT/PUBL/COOK10.PS or from the web 
at http://www.aips.nrao.edu/cook.html.

Eric Greisen