https://casaguides.nrao.edu/index.php?title=Fit_an_arbitrary_sky_(image)_model_to_an_existing_MS&feed=atom&action=historyFit an arbitrary sky (image) model to an existing MS - Revision history2024-03-29T01:10:26ZRevision history for this page on the wikiMediaWiki 1.38.6https://casaguides.nrao.edu/index.php?title=Fit_an_arbitrary_sky_(image)_model_to_an_existing_MS&diff=32063&oldid=prevBmason at 14:46, 15 March 20222022-03-15T14:46:30Z<p></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>split(vis='calibrated_final_cont.ms',outputvis=realmsname,field='4',</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>split(vis='calibrated_final_cont.ms',outputvis=realmsname,field='4',</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div> spw=spwid,combine='scan',timebin='1e8')</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> spw=spwid,combine='scan',timebin='1e8'<ins style="font-weight: bold; text-decoration: none;">,keepflags=False</ins>)</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>fakemsname='calibrated_final_cont_spw'+spwid+'_AVG_MOCK.ms'</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>fakemsname='calibrated_final_cont_spw'+spwid+'_AVG_MOCK.ms'</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>split(vis='calibrated_final_cont.ms',outputvis=fakemsname,field='4',</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>split(vis='calibrated_final_cont.ms',outputvis=fakemsname,field='4',</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div> spw=spwid,combine='scan',timebin='1e8')</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> spw=spwid,combine='scan',timebin='1e8'<ins style="font-weight: bold; text-decoration: none;">,keepflags=False</ins>)</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div></pre></div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div></pre></div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div> </div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">NOTE (added March 2022): you need to be careful with flagged data - the keep flags argument above will eliminate any completely flagged rows (all pols/channels), such as the autocorrelations; but further steps are needed if there are partially flagged rows in the MS.</ins></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Currently there is a mismatch in the way real ALMA data are written and how the CASA simulator identifies antennas, with the result that we need to manually set the telescope name in the MS <b>for 7m data (only)</b>: for most other telescopes this will not be the case. We do this using the table toolkit, which exists in your casa environment as "tb"-- </div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Currently there is a mismatch in the way real ALMA data are written and how the CASA simulator identifies antennas, with the result that we need to manually set the telescope name in the MS <b>for 7m data (only)</b>: for most other telescopes this will not be the case. We do this using the table toolkit, which exists in your casa environment as "tb"-- </div></td></tr>
</table>Bmasonhttps://casaguides.nrao.edu/index.php?title=Fit_an_arbitrary_sky_(image)_model_to_an_existing_MS&diff=32005&oldid=prevBmason at 19:24, 2 March 20222022-03-02T19:24:05Z<p></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 15:24, 2 March 2022</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># Set the INCENTER and INWIDTH for the SPW of interest from the listobs()</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># Set the INCENTER and INWIDTH for the SPW of interest from the listobs()</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div># specifically INCENTER+/-<del style="font-weight: bold; text-decoration: none;">INWIDTH </del>should encompass all channels in the SPW of interest.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># specifically INCENTER +/- <ins style="font-weight: bold; text-decoration: none;">0.5xINWIDTH </ins>should encompass all channels in the SPW of interest.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>util.modifymodel(inimage='myskymap.image',</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>util.modifymodel(inimage='myskymap.image',</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div> outimage='myskymapFixed.image',</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div> outimage='myskymapFixed.image',</div></td></tr>
</table>Bmasonhttps://casaguides.nrao.edu/index.php?title=Fit_an_arbitrary_sky_(image)_model_to_an_existing_MS&diff=32004&oldid=prevBmason at 19:21, 2 March 20222022-03-02T19:21:23Z<p></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 15:21, 2 March 2022</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># Set the INCENTER and INWIDTH for the SPW of interest from the listobs()</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># Set the INCENTER and INWIDTH for the SPW of interest from the listobs()</div></td></tr>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>util.modifymodel(inimage='myskymap.image',</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>util.modifymodel(inimage='myskymap.image',</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div> outimage='myskymapFixed.image',</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div> outimage='myskymapFixed.image',</div></td></tr>
</table>Bmasonhttps://casaguides.nrao.edu/index.php?title=Fit_an_arbitrary_sky_(image)_model_to_an_existing_MS&diff=31922&oldid=prevBmason at 16:04, 25 January 20222022-01-25T16:04:12Z<p></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 12:04, 25 January 2022</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div><pre></div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div><pre></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>tb.open(fakemsname+'/POINTING', nomodify=False) </div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>tb.open(fakemsname+'/POINTING', nomodify=False) </div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>tb.removerows(range(tb.nrows()))</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>tb.removerows<ins style="font-weight: bold; text-decoration: none;">(list</ins>(range(tb.nrows(<ins style="font-weight: bold; text-decoration: none;">)</ins>)))</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>tb.done()</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>tb.done()</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div></pre></div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div></pre></div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>One symptom of the problem is zero predicted visibility values, but it is safe in general to delete the POINTING table. (the pointing table contains where each antenna was pointed as a function of time through the course of the observation -- it is important for OTF or full-stokes mosaicking, but not for simple single field or mosaic imaging cases: in those cases the antennas are all assumed to be pointed at the phase center)</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">Note that the explicit "list()" in the removerows() call above is for python3, which uses lazy evaluation of range(), which is problematic for toolkit calls in casa6+. </ins>One symptom of the problem is zero predicted visibility values, but it is safe in general to delete the POINTING table. (the pointing table contains where each antenna was pointed as a function of time through the course of the observation -- it is important for OTF or full-stokes mosaicking, but not for simple single field or mosaic imaging cases: in those cases the antennas are all assumed to be pointed at the phase center)</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Next we use the simulator toolkit--- which is instantiated in your CASA environment as "sm"--- to generate predicted model visibilities from the model image. Only three calls to sim are needed: one to open the MS; one to set the primary beam (which is done from the telescope name); and one to generate the predicted visibilities.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Next we use the simulator toolkit--- which is instantiated in your CASA environment as "sm"--- to generate predicted model visibilities from the model image. Only three calls to sim are needed: one to open the MS; one to set the primary beam (which is done from the telescope name); and one to generate the predicted visibilities.</div></td></tr>
</table>Bmasonhttps://casaguides.nrao.edu/index.php?title=Fit_an_arbitrary_sky_(image)_model_to_an_existing_MS&diff=31917&oldid=prevAkepley at 23:04, 11 January 20222022-01-11T23:04:56Z<p></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 19:04, 11 January 2022</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>''version 20may2015, written with CASA v4.3.1'' </div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>''version 20may2015, written with CASA v4.3.1'' </div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Versioning note (Jan 2022): In CASA 6, sm is imported as smtool in the standard NRAO CASA installation</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Versioning note (Jan 2022): In CASA 6, sm is imported as smtool in the standard NRAO CASA installation <ins style="font-weight: bold; text-decoration: none;">and simutil is imported as 'from casatasks.private.simutil import simutil'</ins></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>This casaguide illustrates how to fit an arbitrary sky image model to an existing MS. Along the way it illustrates how to "get your hands" on the raw visibility data in the python interface and how to compute the Chi-squared of the visibility data to your given model. This could be useful if you have a set of source models you would like to compare in the UV domain, but the models are too complicated to be handled by the set of models provided in CASA's uvmodelfit() task (note also that the Nordic ARC has developed a more sophisticated UV model fitting tool set called UVMULTIFIT, documented at [http://www.nordic-alma.se/support/software-tools] and [https://arxiv.org/abs/1401.4984]). The methods illustrated here can be used to estimate the <b>scaling</b> and <b>goodness-of-fit</b> of your model to the MS (although for absolute goodness of fit please note the caveat at the end of this page!). They could also be the starting point for a more comprehensive and sophisticated exploration of a set of possible models using the Chi-squared statistic, for instance. The focus of this guide is an ALMA dataset but the techniques are generally applicable. </div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>This casaguide illustrates how to fit an arbitrary sky image model to an existing MS. Along the way it illustrates how to "get your hands" on the raw visibility data in the python interface and how to compute the Chi-squared of the visibility data to your given model. This could be useful if you have a set of source models you would like to compare in the UV domain, but the models are too complicated to be handled by the set of models provided in CASA's uvmodelfit() task (note also that the Nordic ARC has developed a more sophisticated UV model fitting tool set called UVMULTIFIT, documented at [http://www.nordic-alma.se/support/software-tools] and [https://arxiv.org/abs/1401.4984]). The methods illustrated here can be used to estimate the <b>scaling</b> and <b>goodness-of-fit</b> of your model to the MS (although for absolute goodness of fit please note the caveat at the end of this page!). They could also be the starting point for a more comprehensive and sophisticated exploration of a set of possible models using the Chi-squared statistic, for instance. The focus of this guide is an ALMA dataset but the techniques are generally applicable. </div></td></tr>
</table>Akepleyhttps://casaguides.nrao.edu/index.php?title=Fit_an_arbitrary_sky_(image)_model_to_an_existing_MS&diff=31916&oldid=prevAkepley: fixed error in casa information2022-01-10T22:07:46Z<p>fixed error in casa information</p>
<table style="background-color: #fff; color: #202122;" data-mw="interface">
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 18:07, 10 January 2022</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>''version 20may2015, written with CASA v4.3.1'' </div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>''version 20may2015, written with CASA v4.3.1'' </div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Versioning note (<del style="font-weight: bold; text-decoration: none;">August 2021</del>): CASA 6 <del style="font-weight: bold; text-decoration: none;">has moved the functionality of simutil.modifymodel to iatool.modify</del>, <del style="font-weight: bold; text-decoration: none;">and </del>sm is imported as smtool in the standard NRAO CASA installation</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Versioning note (<ins style="font-weight: bold; text-decoration: none;">Jan 2022</ins>): <ins style="font-weight: bold; text-decoration: none;">In </ins>CASA 6, sm is imported as smtool in the standard NRAO CASA installation</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>This casaguide illustrates how to fit an arbitrary sky image model to an existing MS. Along the way it illustrates how to "get your hands" on the raw visibility data in the python interface and how to compute the Chi-squared of the visibility data to your given model. This could be useful if you have a set of source models you would like to compare in the UV domain, but the models are too complicated to be handled by the set of models provided in CASA's uvmodelfit() task (note also that the Nordic ARC has developed a more sophisticated UV model fitting tool set called UVMULTIFIT, documented at [http://www.nordic-alma.se/support/software-tools] and [https://arxiv.org/abs/1401.4984]). The methods illustrated here can be used to estimate the <b>scaling</b> and <b>goodness-of-fit</b> of your model to the MS (although for absolute goodness of fit please note the caveat at the end of this page!). They could also be the starting point for a more comprehensive and sophisticated exploration of a set of possible models using the Chi-squared statistic, for instance. The focus of this guide is an ALMA dataset but the techniques are generally applicable. </div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>This casaguide illustrates how to fit an arbitrary sky image model to an existing MS. Along the way it illustrates how to "get your hands" on the raw visibility data in the python interface and how to compute the Chi-squared of the visibility data to your given model. This could be useful if you have a set of source models you would like to compare in the UV domain, but the models are too complicated to be handled by the set of models provided in CASA's uvmodelfit() task (note also that the Nordic ARC has developed a more sophisticated UV model fitting tool set called UVMULTIFIT, documented at [http://www.nordic-alma.se/support/software-tools] and [https://arxiv.org/abs/1401.4984]). The methods illustrated here can be used to estimate the <b>scaling</b> and <b>goodness-of-fit</b> of your model to the MS (although for absolute goodness of fit please note the caveat at the end of this page!). They could also be the starting point for a more comprehensive and sophisticated exploration of a set of possible models using the Chi-squared statistic, for instance. The focus of this guide is an ALMA dataset but the techniques are generally applicable. </div></td></tr>
</table>Akepleyhttps://casaguides.nrao.edu/index.php?title=Fit_an_arbitrary_sky_(image)_model_to_an_existing_MS&diff=30914&oldid=prevBmason at 14:52, 25 August 20212021-08-25T14:52:44Z<p></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 10:52, 25 August 2021</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>''version 20may2015, written with CASA v4.3.1'' </div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>''version 20may2015, written with CASA v4.3.1'' </div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">Versioning note (August 2021): CASA 6 has moved the functionality of simutil.modifymodel to iatool.modify, and sm is imported as smtool in the standard NRAO CASA installation</ins></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>This casaguide illustrates how to fit an arbitrary sky image model to an existing MS. Along the way it illustrates how to "get your hands" on the raw visibility data in the python interface and how to compute the Chi-squared of the visibility data to your given model. This could be useful if you have a set of source models you would like to compare in the UV domain, but the models are too complicated to be handled by the set of models provided in CASA's uvmodelfit() task (note also that the Nordic ARC has developed a more sophisticated UV model fitting tool set called UVMULTIFIT, documented at [http://www.nordic-alma.se/support/software-tools] and [https://arxiv.org/abs/1401.4984]). The methods illustrated here can be used to estimate the <b>scaling</b> and <b>goodness-of-fit</b> of your model to the MS (although for absolute goodness of fit please note the caveat at the end of this page!). They could also be the starting point for a more comprehensive and sophisticated exploration of a set of possible models using the Chi-squared statistic, for instance. The focus of this guide is an ALMA dataset but the techniques are generally applicable. </div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>This casaguide illustrates how to fit an arbitrary sky image model to an existing MS. Along the way it illustrates how to "get your hands" on the raw visibility data in the python interface and how to compute the Chi-squared of the visibility data to your given model. This could be useful if you have a set of source models you would like to compare in the UV domain, but the models are too complicated to be handled by the set of models provided in CASA's uvmodelfit() task (note also that the Nordic ARC has developed a more sophisticated UV model fitting tool set called UVMULTIFIT, documented at [http://www.nordic-alma.se/support/software-tools] and [https://arxiv.org/abs/1401.4984]). The methods illustrated here can be used to estimate the <b>scaling</b> and <b>goodness-of-fit</b> of your model to the MS (although for absolute goodness of fit please note the caveat at the end of this page!). They could also be the starting point for a more comprehensive and sophisticated exploration of a set of possible models using the Chi-squared statistic, for instance. The focus of this guide is an ALMA dataset but the techniques are generally applicable. </div></td></tr>
</table>Bmasonhttps://casaguides.nrao.edu/index.php?title=Fit_an_arbitrary_sky_(image)_model_to_an_existing_MS&diff=20771&oldid=prevBmason at 19:32, 28 December 20162016-12-28T19:32:01Z<p></p>
<table style="background-color: #fff; color: #202122;" data-mw="interface">
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 15:32, 28 December 2016</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># what are the dims of the data?</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># what are the dims of the data?</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>r2.shape</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>r2.shape</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div># will be [npol,nrows] if no spectral channels or [npol, nchan, nrows] if n_spectral_channels > 1</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># will be [npol,nrows] if no spectral channels </div></td></tr>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># built-in sqrt method does not work elementwise so import numpy's version -</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># built-in sqrt method does not work elementwise so import numpy's version -</div></td></tr>
</table>Bmasonhttps://casaguides.nrao.edu/index.php?title=Fit_an_arbitrary_sky_(image)_model_to_an_existing_MS&diff=20770&oldid=prevBmason at 19:31, 28 December 20162016-12-28T19:31:22Z<p></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 15:31, 28 December 2016</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># what are the dims of the data?</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># what are the dims of the data?</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>r2.shape</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>r2.shape</div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"># will be [npol,nrows] if no spectral channels or [npol, nchan, nrows] if n_spectral_channels > 1</ins></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># built-in sqrt method does not work elementwise so import numpy's version -</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># built-in sqrt method does not work elementwise so import numpy's version -</div></td></tr>
</table>Bmasonhttps://casaguides.nrao.edu/index.php?title=Fit_an_arbitrary_sky_(image)_model_to_an_existing_MS&diff=20769&oldid=prevBmason at 15:36, 28 December 20162016-12-28T15:36:29Z<p></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 11:36, 28 December 2016</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>This casaguide illustrates how to fit an arbitrary sky image model to an existing MS. Along the way it illustrates how to "get your hands" on the raw visibility data in the python interface and how to compute the Chi-squared of the visibility data to your given model. This could be useful if you have a set of source models you would like to compare in the UV domain, but the models are too complicated to be handled by the set of models provided in CASA's uvmodelfit() task (note also that the Nordic ARC has developed a more sophisticated UV model fitting tool set called UVMULTIFIT, documented at [http://www.nordic-alma.se/support/software-tools] and [https://arxiv.org/abs/1401.4984]). The methods illustrated here can be used to estimate the <b>scaling</b> and <b>goodness-of-fit</b> of your model to the MS (<del style="font-weight: bold; text-decoration: none;">*</del>although<del style="font-weight: bold; text-decoration: none;">, </del>for absolute goodness of fit<del style="font-weight: bold; text-decoration: none;">, </del>please note the caveat at the end of this page!). They could also be the starting point for a more comprehensive and sophisticated exploration of a set of possible models using the Chi-squared statistic, for instance. The focus of this guide is an ALMA dataset but the techniques are generally applicable. </div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>This casaguide illustrates how to fit an arbitrary sky image model to an existing MS. Along the way it illustrates how to "get your hands" on the raw visibility data in the python interface and how to compute the Chi-squared of the visibility data to your given model. This could be useful if you have a set of source models you would like to compare in the UV domain, but the models are too complicated to be handled by the set of models provided in CASA's uvmodelfit() task (note also that the Nordic ARC has developed a more sophisticated UV model fitting tool set called UVMULTIFIT, documented at [http://www.nordic-alma.se/support/software-tools] and [https://arxiv.org/abs/1401.4984]). The methods illustrated here can be used to estimate the <b>scaling</b> and <b>goodness-of-fit</b> of your model to the MS (although for absolute goodness of fit please note the caveat at the end of this page!). They could also be the starting point for a more comprehensive and sophisticated exploration of a set of possible models using the Chi-squared statistic, for instance. The focus of this guide is an ALMA dataset but the techniques are generally applicable. </div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The example assumes we have an ALMA 7m MS; we are interested in the continuum data only; and we have a sky model as a FITS image which we wish to compare with the UV data (i.e., the MS). As written, this tutorial requires you to process one spectral window (SPW) at a time. '''It also assumes each SPW has been averaged down to only a single channel''' through appropriate use of the CASA routine split().</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The example assumes we have an ALMA 7m MS; we are interested in the continuum data only; and we have a sky model as a FITS image which we wish to compare with the UV data (i.e., the MS). As written, this tutorial requires you to process one spectral window (SPW) at a time. '''It also assumes each SPW has been averaged down to only a single channel''' through appropriate use of the CASA routine split().</div></td></tr>
</table>Bmason