Detecting and classifying small (i.e., with calibers ranging from 20 to 60 mm) and deep targets (burial depth more than 11 times
targets diameter) is still a challenging problem using current advanced EMI sensors and signal processing approaches. In order to
overcome this problem, the standard time-domain NRL TEMTADS 2x2 electromagnetic induction (EMI) instrument is updated.
Namely, the NRL TEMTADS 2x2 system’s transmitter electronics is modified to increase transmitter (Tx) currents from 6 Amperes
to 14 Amperes. The instrument has a Tx array with four coplanar square coils, together with four tri-axial receivers (Rx) placed at the
center of each Tx. Each Rx cube contains three orthogonal coils and thus registers all three vector components of the impinging
signals. The Tx coils, with transmitter currents of ~14 A, illuminate a buried target, and the target responses are collected with a 500
kHz sample rate after turn off of the excitation pulse. The system operates in both static (cued) and dynamic modes. For cued mode,
the raw decay measurements are grouped into 121 logarithmically-spaced “gates” whose center times range from 25 μs to 24.35 ms
with 5% widths. The sensor is placed on a cart which provides a sensor-to-ground offset of 20 cm or less. In this paper, studies for
APG Calibration, Blind, and Small Munitions Grids are presented and analyzed. The areas are arranged in grids of test cells and the
cell center positions are known. Each target position is flagged with a non-metallic pin flag using cm-level GPS. The sensor is
positioned over each target in turn. With the system positioned over the target, each Tx is activated sequentially and during off the Tx
current, all four Rx record data. The capabilities of this sensor platform is rigorously investigated for UXO classification at APG
blind and small munitions grids.