{"id":9739,"date":"2019-05-29T00:53:47","date_gmt":"2019-05-29T10:53:47","guid":{"rendered":"http:\/\/www.eaobservatory.org\/jcmt\/?p=9739"},"modified":"2020-12-29T11:00:09","modified_gmt":"2020-12-29T21:00:09","slug":"combining-multiple-pol2-fields","status":"publish","type":"post","link":"https:\/\/www.eaobservatory.org\/jcmt\/2019\/05\/combining-multiple-pol2-fields\/","title":{"rendered":"Combining multiple POL2 fields"},"content":{"rendered":"

If you wish to combine POL2 observations for multiple overlapping fields, the best way to proceed is probably as follows (note, for this to work correctly you will need a Starlink build from 9th June 2019 or later):<\/p>\n

    \n
  1. \n
      \n
    1. \u00a0Run “step 1” independently for each field. In other words,\u00a0use pol2map<\/span> to create an auto-masked total intensity map for each field. The following assumes that pol2map<\/span> is run within directories called “field1″, field2”, etc<\/em>, to create the auto-masked maps and the I\/Q\/U time-stream data for each field.<\/li>\n
    2. Co-add the auto-masked total intensity maps for all fields. First create a text file holding the paths to the separate auto-masked total intensity maps, and then run pol2map<\/span> as follows:\n
      % more infiles\r\nfield1\/iauto\r\nfield2\/iauto\r\n% pol2map in=^infiles iout=iauto_mosaic \\\r\n          qout=! uout=! multiobject=yes\r\n\r\n<\/pre>\n<\/li>\n
    3. Run “step 2” and “step 3” for each field, using the mosaic created above as the mask field for all fields. For instance, for the first field:\n
      % cd field1\r\n% pol2map in=qudata\/\\* iout=iext qout=! \\\r\n          uout=! mapdir=maps mapvar=yes \\\r\n          skyloop=yes mask=..\/iauto_mosaic \r\n% pol2map in=qudata\/\\* iout=! qout=qext \\\r\n          uout=uext mapdir=maps mapvar=yes \\\r\n          skyloop=yes mask=..\/iauto_mosaic \\\r\n          ipref=iext cat=mycat debias=yes<\/pre>\n
      Then do the same for field2<\/span>, field3<\/span>, etc<\/em>. If preferred, steps 2 and 3 can be combined into a single invocation of pol2map<\/span>:<\/p>\n
      % cd field1\r\n% pol2map in=qudata\/\\* iout=iext qout=qext \\\r\n          uout=uext mapdir=maps mapvar=yes \\\r\n          skyloop=yes mask=..\/iauto_mosaic \\\r\n          ipref=iext cat=mycat debias=yes<\/pre>\n<\/li>\n
    4. Co-add the external-masked I\/Q\/U maps for all fields and create a vector catalogue from the co-added maps. First create a text file holding the paths to the external-masked I\/Q\/U maps for all fields, and then run pol2map<\/span> as follows:\n
      % more infiles\r\nfield1\/iext\r\nfield1\/qext\r\nfield1\/uext\r\nfield2\/iext\r\nfield2\/qext\r\nfield2\/uext\r\n% pol2map in=^infiles iout=iext_mosaic \\\r\n          qout=qext_mosaic uout=uext_mosaic \\\r\n          multiobject=yes cat=mycat_mosaic \\\r\n          debias=yes ipcor=no<\/pre>\n<\/li>\n<\/ol>\n<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"
      If you wish to combine POL2 observations for multiple overlapping fields, the best way to proceed is probably as follows (note, for this to work correctly you will need a Starlink build from 9th June 2019 or later): \u00a0Run “step 1” independently for each field. In other words,\u00a0use pol2map to\u2026 Continue reading<\/a><\/p>\n","protected":false},"author":13,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[36],"tags":[37],"_links":{"self":[{"href":"https:\/\/www.eaobservatory.org\/jcmt\/wp-json\/wp\/v2\/posts\/9739"}],"collection":[{"href":"https:\/\/www.eaobservatory.org\/jcmt\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.eaobservatory.org\/jcmt\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.eaobservatory.org\/jcmt\/wp-json\/wp\/v2\/users\/13"}],"replies":[{"embeddable":true,"href":"https:\/\/www.eaobservatory.org\/jcmt\/wp-json\/wp\/v2\/comments?post=9739"}],"version-history":[{"count":5,"href":"https:\/\/www.eaobservatory.org\/jcmt\/wp-json\/wp\/v2\/posts\/9739\/revisions"}],"predecessor-version":[{"id":9781,"href":"https:\/\/www.eaobservatory.org\/jcmt\/wp-json\/wp\/v2\/posts\/9739\/revisions\/9781"}],"wp:attachment":[{"href":"https:\/\/www.eaobservatory.org\/jcmt\/wp-json\/wp\/v2\/media?parent=9739"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.eaobservatory.org\/jcmt\/wp-json\/wp\/v2\/categories?post=9739"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.eaobservatory.org\/jcmt\/wp-json\/wp\/v2\/tags?post=9739"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}