Method and apparatus for providing a magnetic direction reference
First Claim
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1. A method of providing a magnetic reference for use in determining direction, the method comprising:
- providing a magnetic observatory device which includes magnetometer means for detecting the direction of the earth'"'"'s magnetic field and telemetry means for transmitting information derived from the magnetometer means to a remote location;
positioning said magnetic observatory device at a fixed first location relative to the surface of the earth;
establishing the orientation of the magnetic observatory device with respect to true North;
deriving from said information the instantaneous variation between true North and magnetic North in the vicinity of said location; and
using said variation in real time at a second location spaced from the magnetic observatory device as a reference in conjunction with locally derived magnetic North information.
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Abstract
A magnetic observatory device is deployed at a fixed location such as the sea bed to provide data measuring variations in the local earth magnetic field. This data is used to correct information from magnetic direction sensors, for example in a measurement-while-drilling system of a drill string. Also described is a reference apparatus for initial calibration of the device or for marine magnetic mapping purposes.
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10 Claims
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1. A method of providing a magnetic reference for use in determining direction, the method comprising:
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providing a magnetic observatory device which includes magnetometer means for detecting the direction of the earth'"'"'s magnetic field and telemetry means for transmitting information derived from the magnetometer means to a remote location;
positioning said magnetic observatory device at a fixed first location relative to the surface of the earth;
establishing the orientation of the magnetic observatory device with respect to true North;
deriving from said information the instantaneous variation between true North and magnetic North in the vicinity of said location; and
using said variation in real time at a second location spaced from the magnetic observatory device as a reference in conjunction with locally derived magnetic North information. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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- 8. A magnetic reference apparatus for use in measuring and establishing the unknown earth'"'"'s magnetic field, the apparatus comprising floatation means supporting the apparatus at the sea surface, magnetometer means responsive to the earth'"'"'s magnetic field to provide output signals representative of the orientation of the apparatus with respect to the earth'"'"'s magnetic field, heading reference means providing a directional reference related to true North, and means for measuring attitude changes of the apparatus during use.
Specification