Abstract: Disclosed is a northfinding apparatus having a single rotation rate sensor secured to a platform. The output of the rotation rate sensor is corrected for tilt and tilt rate of the platform. Measurements of the tilt and tilt rate and the rotation rate are combined to provide an azimuth angle of the platform relative to north.

Abstract: The present invention provides a method and apparatus for removing systematic distortion from measurements of an observable parameter. The method and apparatus of the present invention is particularly useful for removing systematic distortion in phase angle measurements of ring laser angular rate sensors.

Abstract: A data projection system in which a data projector having a data display memory associated therewith projects images to a viewing screen. The system includes a curved or nonplanar viewing screen and computer software effective to provide viewing fidelity by compensating for inaccuracies of the viewing screen.

Abstract: A gyro readout mask is made from the actual readout interference fringe pattern. A photographic image of the readout interference fringe pattern is made, and the resulting photographic image, or a derivative thereof, is itself used as the mask.

Abstract: Navigation by interpretation of images of parallelogram corner points of a ground beacon array. A video camera senses images of the beacon array and a computer interprets the images to provide attitude and location of the platform, on which the camera is mounted, relative to the array.

Abstract: A single-axis rate sensor for determining angular speed .theta. in inertial space of an object rotating about the axis. The rate sensor includes a mass, a motor for rotating the mass about the axis at an angular speed .omega. relative to the object, and a microcomputer for determining a centrifugal force at a radius R from the axis due to the rotation of the mass about the axis at an angular speed .OMEGA. in inertial space, where .OMEGA. is the sum of .theta. and .omega.. Alternative embodiments provide a closed loop system where .OMEGA. is held constant, and a dual rotor arrangement which can be used to reduce a nonlinear factor in a relationship between .theta. and centrifugal force and/or to provide an in-operation self-checking feature.

Abstract: Fluid comsumption is dramatically reduced in hydrostatic support devices by texturing the supporting surface and/or the surface of the object being supported so that a series or constrictions or lossy orifices are provided along the flow path of the supporting fluid. Further, the stability of the supported object is enhanced by the present invention.

Abstract: A path length control for a ring laser is described which captures a true peak power laser mode in the presence of parasitic secondary power modes. The control utilizes a decaying dither of the optical path length which decays from a large initial dither amplitude.

Abstract: Apparatus and method for the surveying of bore holes, for example, oil wells and the like, to permit accurate three-dimensional mapping thereof, using a single rate gyroscope and an accelerometer package in an instrumentation pod which is lowered into the bore hole. Signals from the accelerometers and the rate gyroscope plus the increments by which the pod is lowered into the well permit continual calculation of pod attitude and updated of pod position at all depths in the hole.

Abstract: Apparatus and method for the surveying of bore holes, for example, oil wells and the like, to permit accurate three-dimensional mapping thereof, using an accelerometer package in an instrumentation pod which is lowered into the bore hole. In one embodiment the pod is lowered on the end of a rod string where adjacent rods connected together with Hookes-joint pivots which permit two degrees of freedom of movement between adjacent rods. In another embodiment, rigid interconnections of adjacent rods are used, and the rods are isotropic for twistless flexure as the rods encounter curves in the path of the bore hole. The instrumentation pod is lowered one rod-length at a time, and accelerometer readings are taken which, together with mathematical modeling of rod motion, permits calculation of updated pod position at all depths in the hole.

Abstract: A laser angular rate sensor with a lock-in error cancelling biasing system is disclosed.

Abstract: An orthogonally related target point array is provided in fixed relationship to an object. A photo detector image plane obtains images of the target points projected through a lens located a fixed distance from the image plane. Simple algebraic manipulation of image plane position coordinates of the images corresponding to the target points provides for the establishment of a vector replica of the target point array. The vector replica, in turn, is sufficient data to provide spatial information about the object including position and orientation information with full six-degrees-of-freedom.

Abstract: A target plane in fixed relationship to an object provides a first triad of three collinear target points which lie on a first line projection and a second triad of target points which lie on a second line projection which is in nonalignment with the first triad. A photo detector image plane obtains images of the target points projected on the image plane through a lens located a fixed distance from the image plane. Simple algebraic manipulation of image plane position coordinates of the images corresponding to the target points provides for the establishment of vector replicas of the position of the target points. The vector replicas, in turn, are sufficient data to provide spatial information about the object including position and oriention information with full six-degrees-of-freedom.

Abstract: A discriminant apparatus for a ring laser angular rate sensor is described which provides a discriminant signal indicative of the lock-in rate of the sensor as a function of the phase difference and frequency difference between the counter-propagating waves therein.

Abstract: The present invention provides a discriminant signal apparatus for providing a discriminant signal indicative of the lock-in rate. The discriminant signal apparatus of the present invention is responsive to the behavior of the instantaneous phase difference between the waves, and specifically the behavior of the phase difference occurring substantially about, both before and after, occurrences of the first derivative of the phase difference having substantially zero value.

Abstract: In the present application, a discriminant apparatus for a ring laser angular rate sensor is described which provides a discriminant signal indicative of the lock-in rate of the sensor derived from the phase difference between the counter-propagating waves therein. The discriminant signal may be employed in a closed-loop control signal system for altering the coupling of energy between the counter-propagating waves in a ring laser angular rate sensor for controlling the value of the lock-in rate to a minimum rate.

Abstract: Orthogonal components of electromagnetic field perturbations due to objects characterized by electric or magnetic dipoles are measured along orthogonal axes in a plane. The components are proportional with (3 cos.sup.2 .theta.-1) and (3 cos .theta. sin .theta.), where .theta. is the bearing of the dipole center relative to the device for measuring the field components. .theta. is readily determined from these equations and the range of the object can also be determined from knowledge of the dipole moment.

Abstract: The present invention provides a method and apparatus applicable to ring lasers for modulating scattered waves reflected from the mirrors which define the ring laser optical closed-loop path in such a way to reduce the average error produced by lock-in effects to low levels approaching an average of zero.

Abstract: A discriminant apparatus for laser angular rate sensors which provides an output signal related to a selected weighted vectorial sum of the coupling of energy between counterpropagating waves traveling about a closed-loop path. The discriminant apparatus is utilized in a closed-loop control system for minimizing the lock-in rate of the sensor and/or maintaining and selecting scale factor linearity.

Abstract: An electromagnetic system for determining the orientation including position of a helmet worn by a pilot is disclosed having a transmitting antenna for transmitting electromagnetic field vectors, a receiving antenna for sensing the electromagnetic field vectors generated by the transmitting antenna, and a control apparatus responsive to the sensed electromagnetic field vectors and the transmitted electromagnetic field vectors for determining the compensated orientation of the helmet, the compensated orientation relying upon the rotation matrix determined by a previous solution for the orientation of the helmet.