The wavefield sampled by a two-dimensional (2-D) planar array can be charac
terized by a delayed signal. This correspondence investigates the problem o
f the nonparametric estimation of the delay function (or wavefront) when th
e waveform is narrowband. The wave front is estimated by integrating the lo
cal estimates of the differential time of delay (TOD) of the waveform betwe
en neighboring sensors. The ambiguity of the TOD estimator for the narrowba
nd waveform can be conveniently limited by the a priori search interval for
the cross correlation method. The reconstruction of the wavefronts is form
ulated as a least squares problem that is solved iteratively. Errors of the
solution are quantified, and the contribution caused by noise is shown to
be negligible.