Radio-wave measurements of extensive air showers provide precise determinations of arrival direction, primary energy and the depth of shower maximum, $X_{\mathrm{max}}$.
In this work we investigate a novel method that maps the time dependence of the measured electric field into longitudinal profiles
expressed as functions of atmospheric depth. Using the air shower geometry and radio-wave propagation, each time sample recorded by an observer is associated with a position along the shower axis. The Field-Mapping method was evaluated using detailed ZHAireS simulations of $1~\mathrm{EeV}$ inclined air showers. The resulting profiles exhibit sensitivity to longitudinal shower development and suggest that radio-wave observations contain information beyond the conventional observable $X_{\mathrm{max}}$.

