Multi-Sensor Uxo Detection System

A multi-sensor unexploded ordnance (UXO) detection system has been developed in which the<br>various sensors have been positioned in very close proximity to one another. This system is capable of<br>simultaneously deploying magnetic and electromagnetic sensors, along with real-time decimeter GPS<br>positioning, and real-time data monitoring by a single operator.<br>In one mode of operation, a Geonics EM-63 electromagnetic system is deployed along with a<br>Gem Systems GSMP-40 optically-pumped potassium vapor magnetometer. In this mode, the distance<br>between these two sensors on a rigid platform is approximately 1.5 meters. Positioning coordinates,<br>obtained in real-time, are accurate at the decimeter scale, using a NavCom SF-2050M GPS receiver,<br>which utilizes the StarFire satellite-based augmentation system (SBAS). Data from the electromagnetic,<br>magnetic, and positioning systems are recorded in a laptop computer in real-time, and available on a<br>visual display as profile data plots, and tracking using a map-type display.<br>Electromagnetic and magnetic sensor placement in close proximity is achieved using a secondary<br>electromagnetic transmitting coil operating in tandem with the Geonics EM-63. The magnetic sensor is<br>placed at a null point of the total primary magnetic field generated from the EM-63 transmitter coil and<br>the secondary coil combination. Magnetic field mapping in the vicinity of these coils was accomplished<br>using a magneto-resistive chip, which provided several candidate null positions. Extensive testing of the<br>effect of the secondary transmitter coil on anomalies over known UXO targets provided refinement of<br>the sensor placement. The result of this work is that the sensor platform configuration produces a<br>distortion of total magnetic field intensity anomaly measurements less than 10%. Anomaly shape is<br>only affected to a minimal degree, allowing confidence in resulting computer modeling of these data for<br>target geometry, and hence discrimination.<br>Field testing of the platform and sensors took place at two locations near Albuquerque, New<br>Mexico, and at the U.S. Army Corps of Engineers UXO test bed in Vicksburg, Mississippi. The<br>instrument platform proved to be robust in these field-scale tests, and the value of multi-sensor datasets<br>was apparent upon analyses of these data.