Patent ID: 7730625
Filing Date: 2010-06-08
Classification: E21B,G01V

Abstract:
1. An apparatus for determining a special orientation of a gyroscopically oriented survey tool, comprising: a housing having an axis; three accelerometers mounted in the housing having their respective sensitive axis set orthogonally, a first of the axis being aligned to the axis of the housing, a second of the axis being perpendicular to the first, and a third of the axis being perpendicular to both of the first axis and the second axis; and three gyroscopes mounted pseudo-orthogonally in the housing with their respective sensitive axis set at relative angles of other than 90 degrees, none of the axis of the gyroscopes being mounted parallel to the axis of the accelerometers, such arrangement ensuring that any housing rotation will affect at least two gyroscopes and such arrangement ensuring that any housing rotation about any non-vertical gyroscope axis will affect at least one accelerometer; means for using corroborating data from the accelerometers to correct offset factors of the gyroscopes; means for using corroborating data from the accelerometers to correct scale factors of those of the gyroscopes having a non-vertical sensitive axis; and means for correcting the scale factor of one of the gyroscopes having a vertical sensitive axis by using data from non-vertical gyroscopes whole scale factors have been corrected.