  The LOPES experiment, a digital radio interferometer located at KIT
(Karlsruhe Institute of Technology), obtained remarkable results for the
detection of radio emission from extensive air showers at MHz frequencies.
Features of the radio lateral distribution function (LDF) measured by LOPES are
explored in this work for a precise reconstruction of two fundamental air
shower parameters: the primary energy and the shower Xmax. The method presented
here has been developed on (REAS3-)simulations, and is applied to LOPES
measurements. Despite the high human-made noise at the LOPES site, it is
possible to reconstruct both the energy and Xmax for individual events. On the
one hand, the energy resolution is promising and comparable to the one of the
co-located KASCADE-Grande experiment. On the other hand, Xmax values are
reconstructed with the LOPES measurements with a resolution of 90 g/cm2 . A
precision on Xmax better than 30 g/cm2 is predicted and achievable in a region
with a lower human-made noise level.
