Patent ID: 6868922
Filing Date: 2005-03-22
Classification: E21B,G01V

Abstract:
1. A method of determining a digging position of a digging head for a substantially horizontal boring or trenching method of excavation in a region of a noise magnetic field generated by a nearby current, comprising the steps of: sensing an AC magnetic field radiated from a magnetic field source associated with the digging head by an above-ground magnetic sensor, and calculating at least one of the positions of the magnetic field source from the magnitude and direction of the sensed magnetic field, at least one of the position of said magnetic field source, the tilt angle of said magnetic field source to the vertical direction and the azimuth of said magnetic field source that is its axial direction in a horizontal plane being calculated by using a projective component of said magnetic field, sensed by said magnetic sensor, on a straight body orthogonal to a vector-valued direction of said noise magnetic field.