  We present absorption line strength maps of 48 representative elliptical and
lenticular galaxies obtained as part of the SAURON survey of nearby galaxies.
Using high-quality spectra, spatially binned to a constant signal-to-noise, we
measure four key age, metallicity and abundance ratio sensitive indices from
the Lick/IDS system over a two-dimensional field extending up to approximately
one effective radius. We modify the classical Fe5270 index to define a new
index, Fe5270S, which maximizes the usable spatial coverage of SAURON. Maps of
Hbeta, Fe5015, Mgb and Fe5270S are presented for each galaxy. We use the maps
to compute average line strengths integrated over circular apertures of
one-eighth effective radius, and compare the resulting relations of index
versus velocity dispersion with previous long-slit work. The metal line
strength maps show generally negative gradients with increasing radius roughly
consistent with the morphology of the light profiles. Remarkable deviations
from this general trend exist, particularly the Mgb isoindex contours appear to
be flatter than the isophotes of the surface brightness for about 40% of our
galaxies without significant dust features. Generally these galaxies exhibit
significant rotation. We infer from this that the fast-rotating component
features a higher metallicity and/or an increased Mg/Fe ratio as compared to
the galaxy as a whole. The Hbeta maps are typically flat or show a mild
positive outwards radial gradient, while a few galaxies show strong central
peaks and/or elevated overall Hbeta-strength likely connected to recent
star-formation activity. For the most prominent post-starburst galaxies even
the metal line strength maps show a reversed gradient. (abridged)
