With the aid of the active pulse induction system of the UPEX® 745 P²I the unexploded bomb was able
to be precisely pin-pointed and was then able to be uncovered and defused by the bomb disposal unit.
Used for the locating operation was a 20m x 20m transmitter loop, which was laid out and then remained stationary. Within this transmitter loop the mobile receiver loop (1m x 1m) was moved within a 12m x 8m measuring field and the data from this system was recorded with the aid of the EPAD® system.
In order to permit a direct comparison to be made, the measuring field was also mapped magnetically with the EPAD-M MAGNEX® 120 LW multichannel system.
Comparison of the colour-coded maps from the passive magnetic and active electromagnetic surveying systems makes clear the enormous difference in the way they show the anomaly. Magnetically it would only have been possible to detect this unexploded bomb by bore-hole sounding!
When excavating was carried out at the point indicated on the map a 500 kg unexploded bomb was revealed at a
depth of some 3–4 metres. The principal axis of the bomb lay at right angles to the direction to magnetic north, i.e. the most unfavourable situation for magnetic detection.
We thank the Rhineland-Palatinate Bomb Disposal Unit for giving us the opportunity to apply the new system.
Autor. Frank Ditsch