  Detecting a shallowly buried and elongated object and estimating its
orientation using a commonly adopted co-polarized GPR system is challenging due
to the presence of strong ground clutter that masks the target reflection. A
cross-polarized configuration can be used to suppress ground clutter and reveal
the object reflection, but it suffers from inconsistent detection capability
which significantly varies with different object orientations. To address this
issue, we propose a dual-cross-polarized detection (DCPD) method which utilizes
two cross-polarized antennas with a special arrangement to detect the object.
The signals reflected by the object and collected by the two antennas are
combined in a rotationally invariant manner to ensure both effective ground
clutter suppression and consistent detection irrespective of the object
orientation. In addition, we present a dual-cross-polarized orientation
estimation (DCPOE) algorithm to estimate the object orientation from the two
cross-polarized data. The proposed DCPOE algorithm is less affected by
environmental noise and performs robust and accurate azimuth angle estimation.
The effectiveness of the proposed techniques in the detection and orientation
estimation and their advantages over the existing method have been demonstrated
using experimental data. Comparison results show that the maximum and average
errors are 22.3{\deg} and 10.9{\deg} for the Alford rotation algorithm, while
those are 4.9{\deg} and 1.8{\deg} for the proposed DCPOE algorithm in the
demonstrated shallowly buried object cases. The proposed techniques can be
unified in a framework to facilitate the investigation and mapping of shallowly
buried and elongated targets.
