The SAMI Galaxy Survey: Cubism and covariance, putting round pegs into
  square holes
  We present a methodology for the regularisation and combination of sparse
sampled and irregularly gridded observations from fibre-optic multi-object
integral-field spectroscopy. The approach minimises interpolation and retains
image resolution on combining sub-pixel dithered data. We discuss the
methodology in the context of the Sydney-AAO Multi-object Integral-field
spectrograph (SAMI) Galaxy Survey underway at the Anglo-Australian Telescope.
The SAMI instrument uses 13 fibre bundles to perform high-multiplex
integral-field spectroscopy across a one degree diameter field of view. The
SAMI Galaxy Survey is targeting 3000 galaxies drawn from the full range of
galaxy environments. We demonstrate the subcritical sampling of the seeing and
incomplete fill factor for the integral-field bundles results in only a 10%
degradation in the final image resolution recovered. We also implement a new
methodology for tracking covariance between elements of the resulting datacubes
which retains 90% of the covariance information while incurring only a modest
increase in the survey data volume.
