Patent ID: 9297249
Filing Date: 2016-03-29
CPC Classification: E21B,G01V

Claim Text:
1. A surveying method comprising: (a) using a proton magnetometer to scan a prospective area and identify a magnetically clean surface location; (b) obtaining a first and second global positioning measurements at corresponding first and second surface locations, the first surface location being the magnetically clean surface location identified; (c) processing the first and second global positioning measurements obtained to determine a reference direction between the first and second surface locations; (d) aligning one axis of a tri-axial magnetic field sensor with the reference direction; (e) rotating the magnetic field sensor about the axis aligned with the reference direction; (f) measuring a total magnetic force of the Earth at the first surface location while rotating the magnetic field sensor; (g) selecting a tool face angle of the magnetic field sensor at which the total magnetic force measured is substantially equal to a total magnetic force value for the first surface location obtained using the proton magnetometer; (h) measuring a magnetic field vector of the Earth at the first surface location using the magnetic field sensor oriented at the toolface angle selected; and (i) processing the reference direction obtained and the magnetic field vector of the Earth measured to determine at least one of a magnetic declination and a magnetic inclination of the Earth's magnetic field.