  The surface detector (SD) array of the southern Pierre Auger Observatory will
consist of a triangular grid of 1600 water Cherenkov tanks with 1.5 km spacing.
For zenith angles less than 60deg the primary energy can be estimated from the
signal S(1000) at a distance of about 1000m from the shower axis, solely on
basis of SD data. A suitable lateral distribution function (LDF) S(r) is fitted
to the signals recorded by the water tanks and used to quantify S(1000).
Therefore, knowledge of the LDF is a fundamental requirement for determining
the energy of the primary particle. The Engineering Array (EA), a prototype
facility consisting of 32 tanks, has taken data continuously since late 2001.
On the basis of selected experimental data and Monte Carlo simulations various
preliminary LDFs are examined.
