Abstract: A fluid sphere gyroscope is used as the north-seeking sensing element in a gyrocompass. A sensor responsive to angular deviation of the gyroscope from the horizontal provides a tilt signal which is used to energize heating elements located along the independent spin axis of a rotating fluid mass. Application of a thermal gradient along the spin axis of the fluid mass causes a controlled precession of the gyroscope, thereby compensating for bias and acceleration sensitive drift errors and precessing the gyroscope about a vertical axis in a controlled manner. Rotary transformers permit inductive coupling of the heating elements to the tilt signal and to a power source with minimal disturbing torques.

Abstract: A portable gyroscopic compass surveying device includes means for rapidly aligning the apparatus with respect to geographic north, the north finder itself being operated apart from the associated theodolite on its own low mount. The transfer of the azimuth reference data is accomplished optically by sighting the theodolite telescope on a retro-reflector associated with the north finder. Because the north finder is physically separated from the theodolite, sightings may be made by the theodolite operator while the undisturbed north seeking operation is in process, significantly shortening the total time of operation at each station.

Abstract: A miniature automatically self-aligning azimuth reference employs a floated pendulous gyrocompass device for the rapid determination of geographic north as required for surveying purposes. Fast approximate alignment with north from an initially misaligned condition is effected, while the gyroscope rotor is being run up to speed, using flux valve control. The control is then shifted to a gyrocompassing mode including settling, integration, and driving steps which complete precise alignment.

Abstract: A miniature automatically self-aligning azimuth reference employs a floated pendulous gyrocompass device for the rapid determination of geographic north as required for surveying purposes. Fast alignment with north from an initially misaligned condition is effected in an iterative manner through the action of a unitary vertical-axis magnetic centering-torquer-pick off system employing eddy current forces.