Working with interferometric visibility data.
API currently maps quasi-directly onto the MIRIAD data model since those are the files I'm working with.
An "antpol" specifies a voltage stream fed into a correlator: the combination of a particular antenna and a particular feed on that antenna.
A "basepol" specifies a visibility output from a correlator: the data stream associated with the correlation of two input antpols.
A "feed pol(arization)" is the polarization component sampled by a particular receptor on an radio antenna.
A "vis(ibility) pol(arization)" is the polarization sampled by the cross-correlation of the voltages of two radio receptors.