Our work at the University of Auckland on landmine detection has continued and expanded this year. More than 70 countries have a landmine problem: recent estimates put the total number of mines in the ground at around 60-70 million. Mines maim and kill indiscriminately, and cause economic hardship by denying people the use of their land. Since mines are generally concealed, often by burying, one of the barriers to dealing with them is in knowing where they are. This is especially difficult when mines have low or zero metal content, so that metal detectors are unreliable.

At Auckland we have set ourselves the task of developing technology which will enable us to find buried, non-metallic objects. This year we have been investigating three possible approaches: our original thermal imaging technique, a ground-penetrating radar, and an explosive-sniffer. The sniffer, which is in the early stages of development, uses a technique in which small quantities of the material to be detected are made to stick to a quartz crystal which forms part of an oscillator circuit. The small mass-change produced causes a measurable change in oscillation frequency which indicates the presence of the material (in this case TNT vapour). The radar uses a swept-frequency approach in which a sawtooth frequency sweep is transmitted, and the returning echo is mixed with a fraction of the outgoing signal. The resulting difference frequency, typically at about audio frequency, is a measure of the target range. We have built a prototype radar and used it to get some measurements on buried targets. We are hoping to build an improved version.

Our main effort however continues to go into our thermal imaging system. Unlike most other similar approaches, this uses microwave energy to stimulate the formation of a thermal image of the mine on the surface of the ground. We have had some encouraging results with this approach this year, and have some thermal images which not only show the location of the mine, but also give an idea of its size and shape as well.

Our work has received some significant encouragement over the past year. Individual donations continue to come in. In May 1998, The Economist had an article about us. In July, we were very pleased to receive a grant of $100,000 from the New Zealand Government.

Recently I visited Europe and attended two landmines conferences. The first was at the Joint Research Centre of the European Commission at Ispra, northern Italy. This was a big event with a large number of attendees, and several simultaneous sessions, including workshops, training sessions, and an exhibition. I found the training sessions on thermal imaging, and artificial olfaction, to be helpful, and I made a number of useful contacts, including notably the Canadian Ambassador for Mine Action, Jill Sinclair. The Canadians have this year put $17m into a Centre for Mine Action Technologies, and I had a useful discussion with the Centre's Director, Bob Suart.

The second conference was the Second International Conference on the Detection of Abandoned Landmines (MD98), organised by the Institution of Electrical Engineers and held in Edinburgh. This conference was well-organised and with no parallel sessions it was possible to get to almost everything. I personally found it a very useful conference, although I may have some bias since I was on the organising committee... I presented the results of our thermal imaging work, and was pleased with the reception, particularly the comment of one UK delegate who thought they were the best thermal images he had seen. I also chaired one of the conference sessions, on Electro-Optical Sensors.

Where to from here? The conferences confirmed that we are doing the right kinds of things, but that there is still plenty to be done before we achieve reliable and cost-effective detection. We will continue to improve the three current techniques, and may investigate a fourth method, nuclear quadropole resonance (NQR), which shows promise. We will be setting up a dummy minefield, in which we can bury minelike objects and leave them for lengthy periods before trying to find them. We will try to get our thermal imager to the stage of a field prototype. Above all, I will continue to seek the funding (about $400,000) which would enable us to have a few people working fulltime on this most worthwhile of projects.

Contact: lj.carter@auckland.ac.nz

This article first appeared in ESR Newsletter, November 1998.

Revised 24th February 1999