Optimizing detector trials for humanitarian demining

Abstract

The performance of mine detecting instruments is embedded in the behavior of a complex system. The total reliability is always composed of the intrinsic physical detection capability of the sensor, application/environmental influences and human factors. The intrinsic capability and some application factors can be investigated in laboratory measurements. Human factors, other application factors and the overall reliability, can only be evaluated in blind field trials in which the probability of detection (PoD) and false alarm rate (FAR) are measured statistically. Both of these approaches are included in CEN Workshop Agreement CWA 14747:2003, which standardizes detector testing in Humanitarian Demining. We report here the results of a study to investigate how to optimize such testing. For efficient and statistically valid field trials, the number, types and burial depths of targets, and the number of test lanes, soil types, repetitions and operators need to be carefully chosen. Laboratory results should be used to help construct field trial protocols and also to help distinguish the different contributions to the PoD and FAR, to determine where to improve insufficient performance. In this study, four models of metal detector were tested in three field trials and in the laboratory. The repeatability of the field trials is assessed, taking into account operator training and experience. Results of the laboratory tests are compared with results of the field trials and used to construct a "modular model" of the system, as used in nondestructive testing. The conclusions are, in principle, applicable to trials of other types of sensor.