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uvflag - initial check of flagged data

You should inspect how much data was flagged by the online system. As of March 2007, blanking has been enabled at CARMA, and depending on conditions and the threshold setting chosen in the observing script user-defined parameters, one can easily wind up with too much flagged data. Unflagging should of course be done with caution. Currently the default threshold is 20%, i.e. if more than 20% of the (0.5 second) frames of an integration are blanked, that integration itself is flagged.

 % uvflag vis=cx012.SS433.2006sep07.1.miriad options=noapply flagval=flag
 ...
 Total number of records selected: 95628; out of 95628 records
 Antennas used: 1,2,4,5,6,7,8,9,10,12,13,14,15
 Counts of correlations within selected channels
 channel   
 Good:        5894250
 Bad:         2712270
 wide 
 Good:         392950
 Bad:          180818

Just for the record, this is a very high fraction of flagged data. Normally you might see 0.1-1%. If you have a high percentage of flagged data, you might want to look through the Nightly Report or Observing Logs to discover the cause - antenna out-of-array, Rx problem, etc. If you discover serious data problems not accounted for, you should inform the observers - obs@mmarray.org - who can investigate. Since observers change twice a week, this is a good reason to check on your data quality within a few days.


next up previous contents index
Next: Visual: uvplt, uvspec, varplt, Up: Data Inspection Previous: uvlist
Peter
2009-10-05