  After several generations of interferometers in radioastronomy, wide-field
imaging at high angular resolution is today a major goal for trying to match
optical wide-field performances. All the radio-interferometric, wide-field
imaging methods currently belong to the mosaicking family. Based on a 30 years
old, original idea from Ekers & Rots, we aim at proposing an alternate
formalism. Starting from their ideal case, we successively evaluate the impact
of the standard ingredients of interferometric imaging. A comparison with
standard nonlinear mosaicking shows that both processing schemes are not
mathematically equivalent, though they both recover the sky brightness. In
particular, the weighting scheme is very different in both methods. Moreover,
the proposed scheme naturally processes the short spacings from both
single-dish antennas and heterogeneous arrays. Finally, the sky gridding of the
measured visibilities, required by the proposed scheme, may potentially save
large amounts of hard-disk space and cpu processing power over mosaicking when
handling data sets acquired with the on-the-fly observing mode. We propose to
call this promising family of imaging methods wide-field synthesis because it
explicitly synthesizes visibilities at a much finer spatial frequency
resolution than the one set by the diameter of the interferometer antennas.
