Visualizing Metal Detectors for Humanitarian Demining?

LAMI-Mantra Day

LABORATOIRE DE MICRO-INFORMATIQUE - EPFL

December 5th, 1997

Visualizing Metal Detectors for Humanitarian Demining?

http://diwww.epfl.ch/lami/detec/

Overview

Metal detectors used in humanitarian demining have become more and more refined over the year, bat basically suffer from a very high false alarm rate (metallic debris). These devices may indeed have reached their sensitivity limits, but there are a number of other technical fields in which metal detectors are used with profit to deliver information on the object under study other than a simple ``beep'' when its presence is detected. Research in this direction has started to be carried out in humanitarian demining too, concerning for example:

Sensors other than standard coils (e.g. magnetoresistive or miniature fluxgate);
More ``intelligent'' detectors. Output: metallic object size, depth, type;
Visualizing detectors. Output: metallic object size and shape. The HILTI Ferroscan is an example of a commercially available system, capable of delivering a 2D ``image'' of ferromagnetic objects, developed for civil engineering applications (and therefore not expected to be applicable to humanitarian demining ``as is'').

HILTI Ferroscan System Characteristics and Test Expectations

Differential and multisensor system, basically measuring dB_z/dx. Simple and elegant real-time data processing makes the system quite effective for its intended task (analysis of metallic rebars in concrete).

Best results are expected for ``larger'' ferromagnetic objects, such as shallowly buried non minimum-metal mines or Unexploded Ordnance, which usually have to be differentiated from metallic debris. Suboptimal results are likely for isolated and/or non ferromagnetic objects.

The HILTI Ferroscan Metal Detector (click for enlarged view)

``Sandbox'' tests

Several objects, mostly Unexploded Ordnance, have been tested at different depths in our sandbox. Examples:


PMN AP Mine (diam. 110mm)	Ferroscan image (depth: 1.6cm, area 60x60cm)	BLU 26 "Bomblet" (diam. 65mm)	Ferroscan image (depth: 5cm, area 60x60cm)

Concluding Remarks

The system is practical, but has some ``side effects'' for the visualization of smaller isolated (ferromagnetic) objects, and in presence of edges;
The increased spatial resolution is obtained at the price of decreased depth penetration (as expected);
It remains a potentially interesting approach (for some applications); feedback has also to come from the end users!

Claudio Bruschini is a physicist from the University of Genoa (Italy). He received his degree (``Laurea in Fisica'') in 1992 and is now research assistant at LAMI - EPFL. He has worked in high energy physics in Genoa and at CERN, before becoming involved in sensors for humanitarian demining at DeTeC. His recent interests and activities have included metal detectors (trying to provide the user with additional information), surveying mine detection sensors (``technological watch''), information redistribution, updating some of DeTeC's Web services and keeping contacts with manufacturers and other researchers.

http://diwww.epfl.ch/lami/team/claudiob/
E-mail: Tel: +41 21 693 39 11