Abstract: Apparatus including two two-degree-of-freedom gyroscopes and at least two accelerometers mounted on a turntable on a vehicle. The turntable can be positioned about a vehicle vertical axis in one or the other of two positions 180 degrees apart for alignment. After alignment, the turntable is caged into its zero degree position, and the instruments thereafter operate in a strap-down mode with the yaw, roll and pitch angles of the vehicle computed by computer mechanisms which are sensitive to signals from the gyroscopes and accelerometers.

Abstract: A system for determining orientation or position of a movable supporting structure, such as a vehicle, includes a special inertial sensor unit. This unit includes a single gyroscope hereinafter referred to as a "gyro", with its spin axis mounted in alignment with the sensitive axis of an accelerometer. The gyro and accelerometer are mounted pendulously to rotate only about a single axis which is aligned with a direction of travel of the vehicle or with a projectile launching assembly. In additon to being pendulously mounted as mentioned above, the gyro and accelerometer combination may be rotated relative to their pendulous support, to certain fixed positions, in order to facilitate rapid initial alignment and orientation and pre-mission calibration of the inertial instruments. The pendulously mounted unit is also provided with an optical encoder to indicate the roll angle of the vehicle to which the inertial unit is secured.

Abstract: 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.