The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 14, 1978
Filed:
Sep. 03, 1976
Applicant:
Inventor:
Elwin W Seeley, San Diego, CA (US);
Assignee:
The United States of America as represented by the Secretary of the Navy, Washington, DC (US);
Primary Examiner:
Int. Cl.
CPC ...
G01V / ;
U.S. Cl.
CPC ...
324-6 ; 324-8 ;
Abstract
Method and apparatus for detecting tunnels beneath an area of the earth's rface 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.