Overview of the u = 0 flagging procedure. The top row shows a 100-channel binned empty map with horizontal stripes of one target scan of a NGC 1566 observation on the left, and on the right the corresponding FFT amplitude image, which shows a prominent vertical RFI feature at u = 0. The middle row shows the same plots, but after removal of the u = 0 stripe using our flagging procedure. The bottom row shows two zeroth-moment H I maps of NGC 1566, both created using a simple 2σ intensity cut. The bottom-left panel shows the map with the u = 0 RFI still included. The bottom-right panel shows the same map but with the u = 0 RFI removed.