  We consider a two-stage numerical procedure for imaging of objects buried in
dry sand using time-dependent backscattering experimental radar measurements.
These measurements are generated by a single point source of electric pulses
and are collected using a microwave scattering facility which was built at the
University of North Carolina at Charlotte. Our imaging problem is formulated as
the inverse problem of the reconstruction of the spatially distributed
dielectric permittivity $\varepsilon_\mathrm{r}\left(\mathbf{x}\right), \
\mathbf{x}\in \mathbb{R}^{3}$, which is an unknown coefficient in Maxwell's
equations.
  On the first stage an approximately globally convergent method is applied to
get a good first approximation for the exact solution. On the second stage a
local adaptive finite element method is applied to refine the solution obtained
on the first stage. The two-stage numerical procedure results in accurate
imaging of all three components of interest of targets: shapes, locations and
refractive indices. In this paper we briefly describe methods and present new
reconstruction results for both stages.
