Introduction - Geometrics MetalMapper 2x2 Operation Manual

1. Introduction

This manual is a User's Guide for the Geometrics MetalMapper 2x2 geophysical instrument used for the
detection and characterization of Unexploded Ordnance (UXO). This instrument is based on the Naval
Research Laboratory TEMTADS MP 2x2 Cart system developed over the past several years.
The system uses time domain electromagnetic (TDEM) principles to induce electrical currents in buried
metallic objects and then measures the effects of those currents in receivers on the surface. It has four
(4) co-planar transmitter coils placed in a 2 by 2 square. Each transmitter coil is approximately 35 cm x
35 cm in size. Located in the center of each transmitter coil is a 10 cm x 10cm x 10cm receiver cube,
each one containing three (3) orthogonal coils to measure the fields resulting in 12 different receiver
coils. The receiver coils are oriented in 3-dimensions. The transmitter coils are powered using a bi-polar
half duty cycle and the time decay of the subsurface currents (transients) are measured during time off
of the transmitter coils.
The MetalMapper 2x2 can be used in two collection modes, dynamic or static. Dynamic mode is
collected by pushing the cart over targets in a series of closely spaced parallel lines. Navigation features
in the software direct the user to stay on the correct path. Static mode is collected by moving the
instrument over predefined targets from an anomaly list. This anomaly list can be derived from the
results of a dynamic survey, or from another previous geophysical survey (EM61-MK2 for example).
Data is collected and stored in a HDF5 file format. This format is self-describing and easy to read and
edit with many available free software packages. This manual does not cover any post-processing of the
HDF5 files to invert the data and identify the buried metallic objects.
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