Accession Number : ADD005105

Title :   Method for Determining Changes in Earth Resistivity by Measuring Phase Difference Between Magnetic Field Components.

Descriptive Note : Patent,

Corporate Author : DEPARTMENT OF THE NAVY WASHINGTON D C

Personal Author(s) : Seeley,Elwin W

Report Date : 14 Mar 1978

Pagination or Media Count : 4

Abstract : Method and apparatus for detecting tunnels beneath an area of the earth's surface wherein an oscillator couples a current into a linear conductor at the earth's surface to generate a magnetic field in the earth beneath the area. Phase angle measuring means measures phase difference between the vertical and horizontal components of the magnetic field at selected points along a line parallel to the linear conductor to detect abrupt changes in earth resistivity, changes in resistivity indicating the presence and horizontal position of a tunnel. (Author)

Descriptors :   *Patents, *Magnetic fields, *Tunnels, *Detection, Measurement, Earth(Planet), Test methods

Subject Categories : Magnetic & Electric Fld Detection & Detectors

Distribution Statement : APPROVED FOR PUBLIC RELEASE