PROCEDURE and apparatus for determining true north direction

摘要

The gyroscope operated in a strapdown mode and mounted on a float assembly with its spin axis extending in a vertical direction. The float assembly is free to rotate about any horizontal axis but is constrained from rotating about the vertical to assure an accurate azimuthal reference between the gyroscope and the case in which it is floating. The angle between an azimuthal reference line of the gyroscope and true north is obtained by measuring the amount of torque required to counteract precession of the gyroscope about a horizontal sensitive axis which would occur because of the horizontal component of the rate of rotation of the earth.