flag within a range of u coordinates

[Fil8]

Once binning in channels datacubes show horizontal striping.

This is similar to what seen by Mario Santos in the power spectrum of MeerKAT's visibilities, and is due to some RFI? at u=0 and over all values of v.

as seen in this FFT the 'striped' datacube

Hence we add a module that flags (using casacore) in the U coordinate given a certain range.

[ratt-priv-ci]

Can one of the admins verify this patch?

[paoloserra]

test this please