Measuring and testing – Borehole or drilling
Patent
1996-05-20
1997-02-25
Williams, Hezron E.
Measuring and testing
Borehole or drilling
33304, E21B 4700
Patent
active
056061242
ABSTRACT:
A method for determining orientation of an instrument with respect to earth's gravity. The method includes measuring components of earth's gravity along mutually orthogonal axes. One of the axes is substantially parallel to an axis of the instrument. Tilt of the instrument along two orthogonal axes is measured. One of the tilt axes is substantially parallel to the instrument axis. The instrument is rotated about its axis, and biases of the sensors used to measure the components of earth's gravity perpendicular to the instrument axis are calculated by averaging measurements made by these sensors during rotation. The ratio of gains of these sensors is determined from the range of amplitudes of the output of these sensors during rotation. A roll angle is determined from the bias corrected measurements of components of the earth's gravity perpendicular to the axis. The tilt measurement with respect to the two orthogonal axes is then calibrated by using the calculated roll angle. Gain and offset calibration of all the sensors used to measure the components of the earth's gravity is performed using the calibrated tilt measurements and the orientation is calculated from the gravity measurements after correction for gain and offset of the sensors.
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Bergren Paul A.
Chace David M.
Doyle Mark R.
Evans John T.
Roessler Dennis E.
Fagin Richard A.
Politzer Jay L.
Western Atlas International Inc.
Williams Hezron E.
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