| http://www.w3.org/ns/prov#value | - U.S. Pat. No. 5,680,048, issued Oct. 21, 1997, to W. T. Wollny, discloses a device that detects metallic and non-metallic objects on, flush with, or covered by the ground or other surfaces, or by interfering or obscuring structures or surfaces, using ground penetrating radar, a metal detector and a radiometer.
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