Real-time, limited orientation sensor auto-calibration

A system for acquiring magnetometer and accelerometer data, comprising:

• a down hole tool conveyed on a member;
• at least two orthogonal tri-axial sets of magnetometers and accelerometers disposed on the down hole tool;
• a motor for rotating the member;
• a processor configured to:
• obtain magnetometer and accelerometer measurements from the at least two directional sensors during rotation of the tool by at least 360 degrees around the longitudinal axis of the tool;
• determine a transformation variable using the magnetometer and accelerometer measurements;
• transform standard values of at least one of an earth's magnetic field and an earth's gravitational field into a reference frame of the tool using the determined transformation variables;
• determine a residual measurement error from a difference between the magnetometer and accelerometer measurements and the transformed standard values of the at least one of the earth's magnetic field and the earth's gravitational field;
• select a quality level of the determined residual measurement errors;
• and
• apply the residual measurement error to the obtained measurements when the residual measurement is consistent with the selected quality level.

A system for acquiring data downhole, comprising:

• a downhole tool conveyed on a rotating member;
• a magnetometer disposed on the downhole tool, the magnetometer including at least two directional sensors that are substantially orthogonal to each other and to a longitudinal axis of the member;
• and
• a processor configured to:
• obtain measurements from the at least two directional sensors during rotation of the tool by at least 360 degrees around the longitudinal axis of the tool;
• determine a transformation variable using the magnetometer and accelerometer measurements;
• transform standard values of at least one of an earth's magnetic field and an earth's gravitational field into a reference frame of the tool using the determined transformation variables;
• and
• determine a residual measurement error from a difference between the magnetometer and accelerometer measurements and the transformed standard values of the at least one of the earth's magnetic field and the earth's gravitational field;
• select a quality level of the determined residual measurement error;
• and
• apply the determined residual measurement error to the obtained measurements when the determined residual measurement error are consistent with the selected quality level.

A computer-readable medium having a set of instruction stored therein that are accessible to a processor in order to enable the processor to perform a method, the method comprising:

• receiving measurements from at least two directional field sensors in a borehole, wherein the at least two directional sensors are substantially orthogonal to each other and to a longitudinal axis of the down hole tool during rotation of the tool by at least 360 degrees around the longitudinal axis of the tool, wherein the at least two directional field sensors include a magnetometer and an accelerometer;
• obtaining magnetometer and accelerometer measurements at the tool using the at least two directional field sensors;
• determining a transformation variables using the magnetometer and accelerometer measurements;
• transforming standard values of at least one of an earth's magnetic field and an earth's gravitational field into a reference frame of the tool using the determined transformation variables;
• determining a residual measurement error from a difference between the magnetometer and accelerometer measurements and the transformed standard values of the earth's magnetic field and the earth's gravitational field;
• selecting a quality level of the determined residual measurement error;
• and
• applying the determined residual measurement error to the obtained measurements when the determined residual measurement error are consistent with the selected quality level.