Abstract: This invention relates to mapping or survey apparatus and methods, and more particularly concerns derivation of the azimuth output indications for such apparatus in a borehole from the outputs or output indications of either an inertial angular rate vector sensor (or sensors) and an acceleration vector sensor (or sensors), or a magnetic field vector sensor (or sensors), and from the outputs of an acceleration vector sensor (or sensors). At least one of such sensors in any instrument may be canted relative to the borehole axis. Borehole tilt is also derived.

Abstract: Bore-hole mapping, or surveying, or tool steering in a bore-hole is accomplished using selected combinations of sensors, with sensor signal compensation being provided, in the hole or at the surface. Typical sensors include an angular rate sensor or sensors, a linear acceleration sensor or sensors, and an angular acceleration sensor or sensors. The sensor group is typically rotated in the bore-hole, and the sensors may have selected sensitive axis angularity relative to the travel axis in the bore-hole.

Abstract: This invention relates to mapping or survey apparatus and methods, and more particularly concerns derivation of the azimuth output indications for such apparatus in a borehole from the outputs or output indications of either an inertial angular rate vector sensor (or sensors) and an acceleration vector sensor (or sensors), or a magnetic field vector sensor (or sensors), and from the outputs of an acceleration vector sensor (or sensors). Borehole tilt is also derived.

Abstract: Survey apparatus and method employs a free gyroscope for fast determination of azimuth, free gyroscope alignment being periodically corrected by a rate gyroscope which is periodically rotated for accurate azimuth determination. An accelerometer is also usable in conjunction with the gyroscopes for tilt determination. More generally, method and means is provided for calibrating (initially or periodically) an angle or position reference device.

Abstract: Survey apparatus and method employs one or more rate gyroscopes having spin axis components directed along an instrument travel axis and in also in directions normal to the travel axis, so that when the gyroscope or gyroscopes are rotated, the earth's rate of rotation will be detected, at all latitudes and at all instrument attitudes.

Abstract: Survey apparatus and method employs a free gyroscope for fast determination of azimuth, free gyroscope alignment being periodically corrected by a rate gyroscope which is periodically rotated for accurate azimuth determination. An accelerometer is also usable in conjunction with the gyroscopes for tilt determination.