This study deals with the calculation of the distribution of radiometric errors (noise maps) in the images formed by a two-dimensional aperture synthesis radiometer, specifically the MIRAS and the HUT-2D instruments. MIRAS is a spaceborne Y-shaped interferometric radiometer that will be boarded in the European Space Agency's SMOS Earth Explorer Mission. The HUT-2D is a U-shaped airborne interferometric radiometer under development by the Helsinki University of Technology. The study focuses on the known fact that the cross-correlation of the visibility noise does depend on the shape of the sensor. We investigate this dependence for the Y and the U configurations, taking into account also the results of previous studies on redundancy and tapering.