04710708 is referenced by 332 patents and cites 13 patents.

The location method uses relatively low frequency electromagnetic fields, e.g., 1-1000 Hz, for determining the relative position and/or orientation of a transmitting magnetic dipole antenna by using a vector field receiver. The transmitting antenna for subterranean location, is preferably a single axis, elongated solenoid with a ferromagnetic core. The receiving sensor may be a precise three-axis magnetic field detector of either a magnetometer or search coil type. Measurements are made for one or more positions of either the transmitter or receiver, or with one or more transmitters or receivers. The relative location of the transmitter and the receiver is calculated with respect to some known survey station by a method of successive approximations. The operating frequency is chosen to minimize field distortion from common steel structures, such as pipe, casing or railroad tracks, and to minimize field scattering such as from conducting inhomogeneities in the earth. Either the transmitter or receiver can be operated within metal structures such as casing. The method can be used for location of underground boreholes or pipelines; location of trapped miners; as a means of blind surveying such as in underground mines; or as a means of navigation such as in relatively shallow horizontal or vertical drilling and tunneling or in raise bore mining.

Title
Method and apparatus employing received independent magnetic field components of a transmitted alternating magnetic field for determining location
Application Number
36017
Publication Number
4710708
Application Date
July 23, 1982
Publication Date
December 1, 1987
Inventor
Thomas C Moore
Sunnyvale
CA, US
Louis H Rorden
Los Altos
CA, US
Agent
Harry E Aine
Assignee
Develco
CA, US
IPC
G01G 7/78
G01S 3/02
G01C 21/00
G01B 7/14
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