NAVIGATION DEVICE AND METHOD FOR SURVEYING AND DIRECTING A BOREHOLE UNDER DRILLING CONDITIONS

摘要

A navigation device (16) for surveying and directing a borehole (15) comprises: a first gyro (2) including a first sensitive axis (5) and a second sensitive axis (6); a second gyro (4) including at least a third sensitive axis (7); and a driving unit (9) configured to orient the second gyro (4) in a first mode in a first position in which an earth acceleration (g) dependent error on the second gyro (4) is insignificant and to orient the second gyro (4) in a second mode in a second position in which the third sensitive axis (7) is perpendicular to the first sensitive axis (5) and perpendicular to the second sensitive axis (6).