[alma-config] Last telecon and current simulation work

[Steven]

I'll just summarise my verbal report from the last meeting, and say what my
immediate workplan is.

At the time of the previous telephone conference I had just presented
arithmetic difference images, and we discussed displaying image statistics,
FFTs of difference images,  and fractional difference images. The fractional
difference measures primarily discussed were fidelity image results as
presented by Stephane in his example, and the measures proposed by John
which are a series of ratios of (arithmetic difference image)and (smoothed
model magic blanked at a certain level) which gives rise to a corresponding
series of rms values [This is my understanding of it].

As these measures have very similar implications for scripting an AIPS
implementation, I pressed on with implementing the fidelity image as it was
slightly better specified. I originally intended to present just a few
examples for comment, but progress was better than I expected so I was able
to provide a complete set of C array examples and B array examples for MPD,
CYG and SDC (please ignore bad links to the MAR and M51 cases). These
examples are just a first step so feedback was and is welcomed.

Mark asked about negative values in the Fidelity plots and histograms- these
arise because some of the initial model images have negative values in them,
viz. M51, SDC and CYG. M51 and CYG have negative values which are of the
order of 0.1% of the peak values in absolute terms, but the SDC model has
negative values which are up 5% of the peak value in magnitude. The use of
CLEAN boxes was suggested, and also the use of a prior model for images such
as MAR. I raised the question as to whether or not the denominator in the
fidelity image ( the absolute values of the arithmetic difference image,
truncated at 0.7 x  rms value of the difference image) should use the same
rms value for each of the corresponding ring and spiral cases... and the
answer seems to be no, although some are uneasy with the fidelity image as a
whole rather than the details of its implementation.

I reported that FFTs of difference images can be churned out if necessary.


So bearing all this and the discussions from last Thursday's telecon in
mind, I have a number of things to do...

1) Truncate M51, CYG, SDC model images so that they are greater than or
equal to zero. Someone commented that this would take about an hour, which
is true, but the implication in all this is that the imaging, CLEANing,
calculation of smoothed models, differencing and presentation of results for
these models should be redone as well, which takes considerably longer.
2) Import the 10K (dots) model into AIPS, and create down sampled versions
to avoid registration problems. I may as well put the 10K model through the
same process as the others, as (apart from disk usage and cpu time) the only
overhead it imposes is adding a line to the setup file for each batch job.
3) Archive results from AIPS disks to CD, and also text and PostScript files
used in generation of the webpages.
4) Redo imaging, CLEANing, differencing etc. for B and C resolutions using
M51, CYG, SDC and 10K
5) Perform imaging of M51 and and CYG for D resolution for later combination
with B array results, by way of trying multiconfigurations.
6) Try out DBCON using results of 5)
7) Implement John's metric from his specification.
8) Look at obtaining off-source rms values

Use of CLEAN boxes is still an open issue as is the use of a prior model for
Mars. If the consensus is to do either of these in the current round, I
will, obviously redoing everything for all models consistently.

I also want to get the new AIPS distibution, which will impact on
calculation of scaling factors.

Comments please.

Cheers,
       Steven

Steven Heddle, Newington, Holm Road, Kirkwall, Orkney KW15 1PY
Tel: 01856 877119             Email: steven at heddle97.freeserve.co.uk
Fax: 0870 4039359           URL: http://www.heddle97.freeserve.co.uk