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How the ground radar used in Madeleine McCann search works

4 June 2014 Last updated at 17:38 BST

Police investigating the disappearance of Madeleine McCann have begun using ground-penetrating radar equipment on scrubland in the Algarve.

The equipment is being used to look for signs of disturbed earth. Chris Leech from Geomatrix explains how the device works.

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