An important subset of the pseudo-visibility method is the production of
only the zero spacing. Indeed, the zero spacing is just the total flux of
the observed field-of-view. Hence, if the observed field-of-view is small
enough to fit in the single-dish beam (this is in particular always the
case if 
), a single spectra observed with the single-dish telescope
in the direction of the interferometer phase center may be used as zero
spacing, only a scaling from Kelvin to Jansky is needed. This is the poor
man's solution as only part of the short spacing information is recovered
by this technique.