  The paper aims at proposing the first shape identification and classification
algorithm in echolocation. The approach is based on first extracting geometric
features from the reflected waves and then matching them with precomputed ones
associated with a dictionary of targets. The construction of such
frequency-dependent shape descriptors is based on some important properties of
the scattering coefficients and new invariants. The stability and resolution of
the proposed identification algorithm with respect to measurement noise and the
limited-view aspect are analytically and numerically quantified.
