Abstract: A dual global positioning system (GPS) receiver navigation system. The system of the present invention includes a primary GPS receiver adapted to determine a first position. The primary GPS receiver is certified to a first integrity level and is further adapted to provide GPS navigation data to an external device. The system of the present invention also includes a secondary GPS receiver coupled to the primary GPS receiver. The secondary GPS receiver is certified to a second integrity level having less stringent requirements than the first integrity level. The secondary GPS receiver is adapted to determine a second position and monitor the primary GPS receiver to detect a fault condition by comparing the first position and the second position, such that the GPS navigation data is provided in accordance with the first certification level regardless of the second integrity level of the secondary GPS receiver.

Abstract: The apparatus and method for minimization the residual multipath distortion signal present in the received spread spectrum signal are disclosed. In the preferred embodiment, the apparatus comprises a generator of non-uniform weighting function used for estimation and actual minimization of the residual multipath signal.

Abstract: Method and apparatus for formation of an autocorrelation difference function of an incoming digital signal that reduces the effects of presence of a multipath signal or of noise in an incoming digital composite signal. An incoming digital composite signal, including direct and multipath signals, is received that has a bit value transition interval of length .DELTA..tau..sub.chip. Two or three consecutive bit values b.sub.n-2, b.sub.n-1 and b.sub.n of the direct (ideal) signal are examined. If a test condition for these bit values is satisfied, a first non-uniform weighting function w1(t) is used to compute the contribution of a time interval I.sub.n ={t'.vertline.t.sub.n-1 +.DELTA.<t'.ltoreq.t.sub.n +.DELTA.}, where .DELTA. is a selected time value satisfying 0.ltoreq..DELTA.<.DELTA..tau..sub.chip, to first and second autocorrelation functions AC#(.tau.;E) and AC#(.tau.;L) with respective selected first and second time shifts .tau.=t.sub.E and .tau.=t.sub.L (>t.sub.E).

Abstract: A range pole and in-line detachable battery module assembly including a range pole (10) with an elongated tubular graphite-epoxy range pole shell (102) which has a female cap assembly (108) and a male cap assembly (26) at opposite ends. The male cap assembly (26) includes a central bore (30) formed therethrough for containing an insulator plug (32) to which are attached coaxial electrical contacts (132, 134). The coaxial electrical contacts include a first contact surface surrounded by a second concentric contact surface. The male cap assembly includes an externally threaded stud (28) having a central bore (30) formed therethrough for containing an insulator plug (32) to which are attached pin sockets (67, 68) which contain spring-loaded male pin electrical contacts (34, 36). A detachable battery module (12) includes a tubular battery-module shell (24) which has a male cap (26) at one end.

Abstract: The present invention provides a radio navigation emulating GPS device. In one embodiment, the radio navigation emulating GPS device receives an identifier associated with a conventional radio navaid. The present radio navigation emulating GPS device then retrieves latitude and longitude information corresponding to the received conventional radio navaid from a database. A satellite based position information system generates position information for the aircraft on which the present radio navigation emulating GPS device is disposed. The present radio navigation emulating GPS device then generates navigation information for the aircraft using the retrieved latitude and longitude information and the satellite based position information for the aircraft. The present radio navigation emulating GPS device then presents the navigation information in a manner which emulates the presentation of navigation information generated by a conventional radio navigation device.

Abstract: A method for improving the provision of emergency assistance services for an emergency site. An observer of an emergency event contacts an Emergency Assistance Services (EAS) operator, using a telephone to describe the type of emergency event and any special circumstances present. The EAS operator also receives the present location of the observer, using a location determination system that is connected to the telephone used by the observer. The EAS operator is provided with an electronic map showing the location of the observer and the location of at least one available EAS responder for the type of emergency event that has occurred. The EAS operator determines whether a given EAS responder has the equipment and/or trained personnel required to respond to the emergency event and, from a group of EAS responders who do so qualify, selects an EAS responder who is estimated to be able to reach the emergency site in the shortest time.

Abstract: The delayed correlation receiver for delay-processing the encrypted satellite signals is disclosed. A central station is designed to receive encoded satellite signals using a high gain antenna. The central station extracts the encrypted satellite information and transmits it to the delayed correlation receiver. The delayed correlation receiver receives the encrypted satellite information using the standard satellite antenna and performs the full correlation with the encrypted information received from the central station without requiring the secret encryption keys.

Abstract: The present invention comprises a low-observable radar altimeter augmented GPS (global positioning system) aircraft navigation system. The system of the present invention includes a GPS receiver, an attitude sensor, and a low-observable radar altimeter. The GPS receiver receives GPS signals and determines a position therefrom. The attitude sensor is coupled to the GPS receiver. The attitude sensor is adapted to receive GPS signals and determine a three dimensional attitude of the aircraft therefrom. The low-observable radar altimeter is also coupled to the GPS receiver and is coupled to the attitude sensor. The radar altimeter is adapted to measure an AGL (above ground level) altitude of the aircraft. The radar altimeter measures the altitude by employing a low-observable radar transmitter slaved to the attitude sensor. The radar altimeter uses the attitude sensor to maintain a radar beam in a substantially vertical attitude (e.g., parallel to the local gravity vector).

Abstract: According to one embodiment, a slope of a land mass is precisely monitored. Remote sensors are placed in selected positions on the slope. The remote sensors are configured to provide real time position information. A virtual model of the slope is created using positioning information generated by the remote sensors and is stored in a computer memory. The position of each remote sensor is also recorded in the computer memory so that the virtual model accurately reflects the real world situation. A threshold value is set to establish a permissible deviation of each remote sensor location. Real time positioning information produced by the remote sensors is monitored at a base station and is used to update the virtual model. If the position of a remote sensor deviates beyond its associated threshold value, an alarm message is flashed. The information so obtained can also be displayed to a user as a graphical and textual representation of the current state of the slope.

Abstract: A battery-operated navigation satellite receiver with an antenna, a radio frequency stage, a down-converter, a digital signal processor and a microcomputer for demodulating L-band microwave carrier frequency spread spectrum transmissions from orbiting navigation satellites that each use their own unique pseudo-random number spreading code. The digital signal processor and a microcomputer each receive system clocks that can be varied in steps from full-speed down to any number of fractions including zero, or full stop. The system clocks to the digital signal processor and a microcomputer are lowered during periods of little or no acquisition or navigation activity. Scheduled updates, communication traffic, user activity, etc., are used to ramp the system clocks back up when the processing load demands it, e.g., when the tasks become CPU-bound at the current clock speed or when a particular task is predetermined to need the full processing speed capability of a particular navigation receiver.

Abstract: The apparatus and method for minimization the residual multipath pseudorange error signal present in the received composite spread spectrum signal are disclosed. In the preferred embodiment, the apparatus comprises at least two tracking channels. Each tracking channel includes a generator of a time-varying non-uniform weighting function. Each tracking channel processes an incoming composite signal and outputs a satellite signal and a multipath pseudorange error signal. The tracking channel output signals are scaled by the computer and combined to yield the output signal comprising a satellite signal and a minimized multipath pseudorange error signal in the area of small delays.

Abstract: The present invention discloses the apparatus and the methods for calibrating a Narrow Band receiver for the group delay code phase errors. The group delay code phase errors are caused by group delay variations in the satellite signals being transmitted by a Narrow Band satellite Transmitter. A Calibration generator circuit generates a calibration signal that is substantially similar to the satellite signal but is free from the group delay variations. The calibration signal is used by the Narrow Band satellite Receiver to measure and eliminate the code phase group delay errors.

Abstract: A GPS navigation receiver channel tracks satellites' Doppler frequencies sequentially during the twenty milliseconds that the signal is coherent in each bit time of the navigation data modulation. It measures frequency by differencing the angles of signal-vector sums weighted by parabolic humps, exploiting the commutativity of linear processing operations to raise the signal-to-noise ratio before the nonlinear operation phase of detection.

Abstract: The mobile unit equipped with the satellite positioning system augmented by the laser positioning system is disclosed. The usage of the satellite positioning system allows the user to determine the coordinate of the laser reflectors prior to the range measurements. The range measurements are performed by the navigational computer using the laser scanning and rotating beam to obtain the range data between the mobile unit and a plurality of laser reflectors, and using the satellite positioning system to obtain the range data between the mobile unit and a plurality of visible navigational satellites. The obtained range data and the laser reflector coordinate data allows the user to perform the navigation of the mobile unit.

Abstract: A system and method for dispatcher free vehicle allocation. In one embodiment, the present dispatcher free vehicle allocation (DFVA) system includes a plurality of mobile service providers (vehicles). Each of the vehicles is communicatively linked to DFVA computer system. Each of the vehicles contain a position determining system adapted to determine the present position of each the vehicle. Each of the vehicles communicates its present position to the DFVA system. The DFVA system is adapted to track the present location of each vehicle. The DFVA system answers dispatch requests for service from customers within the operational area. The DFVA system then determines a most appropriate vehicle of the plurality of vehicles, to respond to the customer's dispatch request. The present DFVA system then transfers the customer to the driver of the most appropriate vehicle.

Abstract: A method and an apparatus using a low Earth orbiting (LEO) satellite signal to augment the Global Positioning System (GPS) for finding a location vector between a GPS user receiver and a GPS reference receiver. The GPS user receiver computes a LEO user-reference carrier phase difference and a GPS user-reference carrier phase difference for the LEO satellite signal and a GPS satellite signal, respectively, received simultaneously at the GPS user receiver and the GPS reference receiver. Carrier phase double differences are computed from a difference between the GPS user-reference carrier phases from two GPS satellites and either the LEO user-reference carrier phases from two LEO satellites or the GPS user-reference carrier phase from one GPS satellite and the LEO user-reference carrier phase from one LEO satellite. The location vector is computed from a difference between the double differences for two satellite geometries.

Abstract: A precision approach capable dual differential global positioning system (DGPS) receiver avionics system. The system of the present invention includes a first and a second DGPS receiver. The first and second DGPS receivers are both adapted to interface with an autopilot in an aircraft. The DGPS receivers each determine the position of the aircraft as the aircraft proceeds along a flight path. Both DGPS receivers are further adapted to employ carrier aiding to smooth the code phase measurements used in determining the position of the aircraft. Within a predetermined range along the approach path of the aircraft and when the output of the first DGPS receiver and the output of the second DGPS receiver are proximate within a predetermined distance, the DGPS receivers determine a transition point. After the transition point, the DGPS receivers utilize DGPS carrier phase tracking to determine the position of the aircraft relative to its position at the transition point.

Abstract: A task description is stored in a database accessible by a mobile computer system. The mobile computer system receives positioning information corresponding to its geographic location and indexes the database based on the positioning information when the information indicates that the mobile computer system is in a geographic location that facilitates completion of a task associated with the task description. The database may be resident in the mobile computer system or accessible in other ways, for example, via the Internet. The task description preferably includes a geocode which corresponds to the geographic location at which completion of the task may be facilitated. The task description may also include textual, voice or other message which can be displayed and/or played back to a user. The positioning information may be obtained from a GPS satellite, a GLONASS satellite or a pseudolite. The mobile computer system may be a portable unit, such as a PDA, or integrated within a vehicle.

Abstract: A method for obtaining integer ambiguity solutions based on externally provided constraints, e.g., altitude. Such constraints are useful in reducing the computational burden created by the search problem, and using constraints is particularly more effective when a more limited number of satellite vehicles are visible than is ordinarily the case. The constraints are exercised in a search algorithm. As the branches of the integer ambiguity search tree are traversed, an additional test is used to determine if the current search candidate is compatible with such external constraint. Because a three-dimensional position is associated with each search candidate, the branch clipping is straightforward. The ambiguity candidates are each only acceptable if their locations in space are within a confidence region bound set determined from the external constraint.

Abstract: A first receiver computes its position using data from sources chosen according to conditions at a second receiver and reference data. The computed position is compared with a known position. The data may be GPS positioning data from satellites and/or pseudolites and the reference data may be RTK GPS data provided by an RTK GPS reference station. The conditions at the second receiver generally correspond to satellite constellations and other parameters and the position of the first receiver may be computed by configuring the first receiver to mimic the conditions at the second receiver. The comparison of the computed position to the known position may result in an error measurement which may be used to initiate an alert condition. In a further embodiment, a receiver has first circuitry configured to compute its position using data from sources chosen according conditions at a remote receiver and reference data.