[alma-config] Teleconference 31 Jan 2001 at 1600UT?

[Al Wootten]

Copy with more extended text and hyperlinks at
http://www.cv.nrao.edu/~awootten/html/almaconfig4jan01min.html

Next teleconference 31 Jan 2001 at 1600UT?  Comments?

Minutes of Meeting 4 Jan 2001

Attendees: Wootten, Guilloteau, Pety, Gueth, Webster, Heddle, Morita,
Conway, Yun, Butler, Kogan, Wright

Next Meeting

Another phone meeting was suggested, to discuss the metrics.
Date: 31 Jan 2001 at 1600UT?


PDR

Since the teleconference, both Lee Mundy (lgm at astro.umd.edu) of the
University of Maryland BIMA Group, and Eric Anterrieu
(Eric.Anterrieu at cerfacs.fr) of (Signal & Image Processing Team), CERFACS, at
Toulouse have agreed to serve as external referees.  Mel Wright has also
been invited.

Simulations

There was considerable discussion on the error images and statistics which
Steven has placed at his WWW site. Steven distributed his report.

Metrics

John suggested that we arrive at the metric iteratively and collected the
emails to alma-config on the subject. Summary of discussions at the
teleconference:

Principle: The metric should not depend on the character of the array.

It was generally agreed that negative values should be suppressed in some
way. There was general agreement that model image pixels could be magic
value blanked at some percentage of the peak, then one could divide the
model and produced images to obtain fractional error and fidelity indeces.
The 'median fidelity' could be extracted at percentages of the peak--1 per
cent, ten per cent, and so on. Then this and fractional error can be plotted
as a function of which percentage was used in the model image The rms for an
image could be defined as the mean from the whole difference image over a
region where there is signal, e.g. the unblanked region. This is covered
in Steven's items 1 and 4.

Discussion also centered on how to treat the fact that differing content of
short spacings dominates the images. This could be addressed by adding in
data from a smaller array. It was decided that it would be excellent if
Heddle were to simulate some multiconfiguration images, including B and D
array data, for e.g. M51 and Cygnus models images. This is item 5 on
Heddle's list.

Since then, there has been some discussion on the dots image.  There are
ALMA simulations with FITS images at:
http://www.cv.nrao.edu/~awootten/mmaimcal/newzlines.html
or John has distributed his DOTS image.  Steven is working on the latter.

Bryan has made an attempt to summarize metric discussion which I understand
he will distribute shortly.