Patent ID: 8781744

Claim:
A method for obtaining information regarding a magnetic field within a first wellbore, the method comprising: receiving at least one first signal from a first magnetic sensor and at least one second signal from a second magnetic sensor, the first magnetic sensor and the second magnetic sensor mounted in a downhole tool within the first wellbore and spaced apart from one another by a non-zero distance, the at least one first signal generated in response to magnetic fields of the Earth and of at least one magnetic region of the downhole tool, the at least one second signal generated in response to magnetic fields of the Earth and of the at least one magnetic region of the downhole tool; calculating information regarding the magnetic field within the first wellbore in response to the at least one first signal from the first magnetic sensor and the at least one second signal from the second magnetic sensor; and using the calculated information regarding the magnetic field to calculate an estimate of an orientation of the downhole tool with respect to the magnetic field of the Earth corrected for interference from the magnetic field of the at least one magnetic region of the downhole tool.