Because handheld systems are lightweight, compact, portable, and deployable under most site conditions, they are particularly useful in areas of dense vegetation or challenging terrain. In heavily wooded areas or areas with steep or uneven terrain, handheld sensors may be the only suitable device for UXO detection and discrimination because they can be carried through spaces that the operator can walk through or at least approach. Furthermore, it is desirable to find and characterize a metallic object without the need to accurately locate the sensors at multiple positions around the target. The ideal system would thus locate and characterize the target from a single position of the sensor and indicate to the operator where to flag the target for subsequent study. The objective of this project was to design and build a prototype handheld UXO discriminator.

The researchers have successfully designed and built the cart-mounted Berkeley UXO Discriminator (BUD) and demonstrated its performance at various test sites. The handheld prototype design incorporates key features of the cart-mounted system – three orthogonal transmitters and ten pairs of receivers, and difference or gradient measurements that significantly reduce ambient and motion noise and greatly enhance sensitivity to the gradients of the target. The system characterizes the target from a single position.

Researchers designed and built a sensor package in the shape of a 14-in (0.35 m) cube. Performance of the system was demonstrated under realistic survey conditions at a test site located at Aberdeen Proving Ground (APG), Maryland. The same discrimination capabilities afforded by the cart-mounted system are available in the handheld unit, although with a slightly reduced depth of detection. If only single objects are present, taking the measurements 0.15 m before and after, and at the item location, along the survey lines resulted in less than 10% of locations that could not be analyzed, while correctly discriminating all munitions with the signal-to-noise above the threshold. Although only 7% of the soundings used in the discrimination were from locations different from the flag locations, having three measurements per anomaly helped with the data quality control, and they were essential especially when a person other than the one interpreting the data acquired the data. This process simplifies the field data acquisition and makes surveys more efficient. If anomaly locations were to correspond to multiple objects, however, multiple measurements around the anomaly would be required to identify them correctly.

The handheld UXO discriminator is well suited for areas with difficult terrain and vegetation or small areas where cart-mounted systems are impossible to use. Furthermore, the device can discriminate objects during the first survey, eliminating a second, cued discrimination survey.