You should always check if you need to (re)apply baseline corrections6.5. Although your data may come with a pretty decent baseline solution, often a few weeks into a new array configuration improved baselines will become available. In the first few days up to several weeks after a move, baselines can settle and may need to be re-applied from the newly computed ones. Normally these are stored in a small ascii table with equatorial values in nanoseconds. (cf. uvgen baseunit=1). Antpos datafiles can be found6.6at http://cedarflat.mmarray.org/observing/baseline/, as well in your local MIRIAD distribution in $MIRCAT/baselines/carma6.7
To apply a new baseline, apply the program uvedit to your multisource data set. Be sure to apply the new baseline to all sources (but not the NOISE source):
uvedit vis=xxx.mir out=yyy.mir apfile=$MIRCAT/baselines/carma/antpos.070115
In rare cases, a new and better solution is found a month or so after your data were taken. Check the status of the baseline solution on the above mentioned web page. It is a good idea to apply an appropriate solution if you are not sure which solution has been applied to your data. No harm is done if you apply a solution that has already been applied.
Notice that for data taken during a move (which can take several days and the array will be in some hybrid configuration) an antpos file will be available for each day. Please check the time validity carefully, either by filename, or comments in the file.
Errors due to baselines can be seen as slopes in phase vs. time. See Figure ...
You can also visually check how much the baselines changed from what is available in your visibility dataset, by comparing the X-Y-Z values (in nsec) in the antpos file with what listobs produced.