US4393350A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for rapidly detecting subterranean tunnels by detecting a non-null value of a resultant horizontal magnetic field component
Assignee: United States Department of the Navy
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Filing: 1981-05-18
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Granted: 1983-07-12
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Expires: 2001-05-18
Abstract
Abstract Method and apparatus for detecting tunnels, voids or other anomalies bene an area of the earth's surface wherein an oscillator couples a current into two conductors laid parallel to each other to generate two magnetic fields in the earth beneath the area. The magnetic field is measured along a line midway between the two horizontal conductors to detect for an increase in the measured field which is an indication of the presence of an anomaly.
Inventors
- 👤 Peder M. Hansen
- 👤 John G. Hoffman
- 👤 Elwin W. Seeley
- 👤 Wesley A. Andrew
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 09:58
CPC Classifications
G; G01; G01V; G01V3/00; G01V3/08
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
121 words
A method for rapidly detecting subterranean tunnels using primary magnetic fields generated by electrical conductors placed on the earth's surface in a manner such that the conductors are parallel and the lenghts thereof are several times greater than the distance separating them comprising the steps of: generating two separate ac primary magnetic fields at a predetermined frequency in a manner that the resultant horizontal component of the magnetic fields along a preselected line on the earth's surface is a null when the surrounding region is characterized with homogeneous electromagnetic properties; measuring said resultant horizontal component of the magnetic fields along said preselected line; and detecting the occurrence of a nonnull measurement as an indication of the location of a subterranean tunnel.
Claim 2
Independent Claim
121 words
A method for rapidly detecting subterranean tunnels using primary magnetic fields generated by electrical conductors placed on the earth's surface in a manner such that the conductors are parallel and the lenghts thereof are several times greater than the distance separating them comprising the steps of: generating two separate ac primary magnetic fields at a predetermined frequency in a manner that the resultant horizontal component of the magnetic fields along a preselected line on the earth's surface is a null when the surrounding region is characterized with homogeneous electromagnetic properties; measuring said resultant horizontal component of the magnetic fields along said preselected line; and detecting the occurrence of a nonnull measurement as an indication of the location of a subterranean tunnel.
Claim 3
Independent Claim
103 words
A method for rapidly detecting subterranean tunnels comprising the steps of: placing a single conductor on the surface of the earth in a manner that two parallel sides are formed with lengths several times greater than the distance separating them; feeding an alternating electric current to the conductor at a preselected frequency; measuring the horizontal component of a resultant magnetic field created by the electric current in the conductor, said measurement occurring on the earth's surface along the centerline between the two parallel sides of the conductor; and detecting a nonnull magnetic field value as evidence of the location of a subterranean tunnel.
Claim 4
Independent Claim
103 words
A method for rapidly detecting subterranean tunnels comprising the steps of: placing a single conductor on the surface of the earth in a manner that two parallel sides are formed with lengths several times greater than the distance separating them; feeding an alternating electric current to the conductor at a preselected frequency; measuring the horizontal component of a resultant magnetic field created by the electric current in the conductor, said measurement occurring on the earth's surface along the centerline between the two parallel sides of the conductor; and detecting a nonnull magnetic field value as evidence of the location of a subterranean tunnel.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-07-11 | 1987-01-10 | 1987-07-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-07-11 | 1991-01-10 | 1991-07-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-07-11 | 1995-01-10 | 1995-07-12 | $7700.00 | Window Closed / Lapsed |