  In most high energy cosmic ray surface arrays, the primary energy is
currently determined from the value of the lateral distribution function at a
fixed distance from the shower core, r0. The value of r0 is mainly related to
the geometry of the array and is, therefore, considered as fixed independently
of the shower energy or direction. We argue, however, that the dependence of r0
on energy and zenith angle is not negligible. Therefore, in the present work we
propose a new characteristic distance, which we call ropt, specifically
determined for each individual shower, with the objective of optimizing the
energy reconstruction. This parameter may not only improve the energy
determination, but also allow a more reliable reconstruction of the shape and
position of rapidly varying spectral features. We show that the use of a
specific ropt determined on a shower-to-shower basis, instead of using a fixed
characteristic value, is of particular benefit in dealing with the energy
reconstruction of events with saturated detectors, which are in general a large
fraction of all the events detected by an array as energy increases.
Furthermore, the ropt approach has the additional advantage of applying the
same unified treatment for all detected events, regardless of whether they have
saturated detectors or not.
