Hanning Smoothing

CASA Modification Request 30C108, November 2007

1. Introduction

Hanning smoothing and other selection u-v channel convolutions are needed to suppress sidelobes from strong line sources and to modify the frequency resolution of a data base.

2. Background

3. Requirements

The convolution and smoothing of a spectral line u-v data base is needed for many spectral line applications. The output of the 'smoothed' data base may or may not contain a smaller number of channels, depending of the type of convolution.

4. Design

Hanning smoothing replaces the frequency channel data in each channel with a three channel running average of the preceding, current and suceeding channels weighted 1/4, 1/2 and 1/4. The first and last channels are flagged. A Python script implementing this algorithm written by David Whysong was provided by Steve Myers.

The toolkit method ms.hanningsmooth has been added to support Hanning smoothing of the frequency channel data. It is accessible via the task hanningsmooth.

5. Deployment Checklist

Modifications to ms.xml, ms_cmpt.* and MSVis/VisSetUtil.* have been checked into the svn repository for inspection and feedback from the sponsor.

An Hanning smoothing task has been checked into the svn repository and is ready for testing.

6. Test Plan

6.1 Internal Testing

6.2 Sponsor Testing

There are several hydrogen line observations that are now being observed with the EVLA. Juergan Ott has been working with George on the development of Hanning smoothing and should work with Crystal Brogan on testing the software as it is being developed.

6.3 Integration/Regression Tests

One of the regression scripts could include hanning smoothing as one of the last reductions steps.

6.4 Testing for Scientific Validity

Comparison with similar processing in AIPS is a good method for validation.


APPROVED: I acknowledge that my request is fully contained in this MR, and if the CASA development group delivers exactly what I specified, I will be happy.

ACCEPTED: I acknowledge that I have validated the completed code according to the acceptance tests, and I am happy with the results.

Written - - - - -
Checked - - - - -
Approved by Scientific Sponsor - - - - -
Accepted/Delivered by Sponsor - - - - -

  • Use %X% if MR is not complete (will display ALERT!)
  • Use %Y% if MR iscomplete (will display DONE)

Discussion Area

-- NicoleRadziwill - 30 Oct 2007

-- EdFomalont - 06 Nov 2007

-- EdFomalont - 07 Nov 2007

-- EdFomalont - 08 Nov 2007
Topic revision: r4 - 2008-01-22, RaymondRusk
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