Abstract: A GPS receiver having a fast acquisition of a GPS signal having a low signal-to-noise ratio. The GPS receiver uses an adjustable local frequency for iteratively downconvertig raw GPS signal samples to baseband GPS signal code data, combining a plurality of code epochs of the GPS signal code data in chunks and superchunks for providing representative code epochs, and correlates the representative code epochs to a replica code epoch for providing correlation times. Two or more correlation times are used to determine a correlation time difference. The correlation time difference is indicative of a residual frequency error. The error is used for correcting the local frequency. GPS pseudoranges are computed from the correlation times when the residual frequency error from the corrected local frequency is below a threshold.

Abstract: A system using coarse GPS orbital parameters for providing a precise GPS location. The system includes a GPS reference receiver and a GPS user receiver. Coarse locations-in-space of GPS satellites are computed from almanac or old ephemeris data. In a first embodiment the GPS user receiver uses DGPS corrections based upon the same coarse orbital parameters for providing a precise DGPS user location. In a second embodiment the GPS user receiver computes a coarse location from the coarse orbital parameters; and the GPS reference receiver recalculates the user pseudoranges using the same coarse orbital parameters and then uses the recalculated user pseudoranges for providing a more accurate user location.

Abstract: A differential global positioning system (DGPS) using coarse data for the locations-in-space of GPS satellites for ranging to the GPS satellites and then determining a precise differentially corrected GPS location of a GPS user receiver. The coarse GPS data can be GPS almanac data or non-current GPS ephemeris data as long as the same data is used by both a GPS reference receiver and the GPS user receiver.

Abstract: A GPS receiver having a fast acquisition of a GPS signal having a low signal-to-noise ratio. The GPS receiver adjusts a local frequency for iteratively downconverting raw GPS signal samples to baseband GPS signal code data, combining a plurality of code epochs of the GPS signal code data in chunks and super chunks for providing representative code epochs, and correlates the representative code epochs to a replica code epoch for providing correlation times. A microcontroller processes the correlation times for providing the frequency corrections and computes a GPS pseudorange when the error in the corrected local frequency is less than a threshold. The GPS pseudoranges for several GPS satellites are transmitted back to the base for computing the GPS-based location of the GPS receiver.

Abstract: A system using coarse GPS orbital parameters for providing a precise GPS location. The system includes a GPS reference receiver and a GPS user receiver. Coarse locations-in-space of GPS satellites are computed from almanac or old ephemeris data. In a first embodiment the GPS user receiver uses DGPS corrections based upon the same coarse orbital parameters for providing a precise DGPS user location. In a second embodiment the GPS user receiver computes a coarse location from the coarse orbital parameters; and the GPS reference receiver recalculates the user pseudoranges using the same coarse orbital parameters and then uses the recalculated user pseudoranges for providing a more accurate user location.

Abstract: A DGPS system using GPS almanac data for determining the locations-in-space and the DGPS corrections for GPS satellites for providing a differentially corrected location of a remote GPS user receiver. A GPS reference receiver determines almanac-based DGPS corrections from the differences between ranges that are measured to GPS satellites and ranges that are calculated to the GPS almanac-based locations-in-space of the GPS satellites from the known location of the GPS reference receiver. The GPS user receiver measures pseudoranges to the GPS satellites. Then, in a first embodiment, the GPS reference receiver radios the DGPS corrections to the GPS user receiver. The GPS user receiver uses almanac-based locations-in-space for the GPS satellites and the almanac-based DGPS corrections for differentially correcting the measured user pseudoranges for providing a differentially corrected user location. In a second embodiment, the GPS user receiver radios the measured user pseudoranges to the GPS reference receiver.

Abstract: A DGPS system using GPS almanac data for determining the locations-in-space and the DGPS corrections for GPS satellites for providing a differentially corrected location of a remote GPS user receiver. A GPS reference receiver determines almanac-based DGPS corrections from the differences between ranges that are measured to GPS satellites and ranges that are calculated to the GPS almanac-based locations-in-space of the GPS satellites from the known location of the GPS reference receiver. The GPS user receiver measures pseudoranges to the GPS satellites. Then, in a first embodiment, the GPS reference receiver radios the DGPS corrections to the GPS user receiver. The GPS user receiver uses almanac-based locations-in-space for the GPS satellites and the almanac-based DGPS corrections for differentially correcting the measured user pseudoranges for providing a differentially corrected user location. In a second embodiment, the GPS user receiver radios the measured user pseudoranges to the GPS reference receiver.

Abstract: Method and apparatus for monitoring the present location of a person (“confinee”) who is to be confined to a designated site, which site can have a diameter as small as a few meters or as large as several kilometers. The present location of the confinee is checked at selected time intervals with time periods ranging from one second to thousands of seconds, as desired. The confinee wears a location-determining (“LD”) unit that receives electromagnetic signals that contain information allowing determination of the present location of the LD unit, and thus of the confinee, from three or more non-collinear outdoor LD signal sources and from three or more non-collinear indoor LD signal sources. The indoor LD signal sources may be radiowave transmitters. The outdoor LD signal sources may be transmitters for a Loran, Omega, Decca, Tacan, JTIDS Relnav or PLRS or similar ground-based system, or transmitters for a satellite positioning system, such as OPS or GLONASS.

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: A precision equivalent landing system. In one embodiment, a position determining system is coupled to an aircraft. The position determining system generates lateral position information of the aircraft with respect to a landing approach path. An altimeter is also coupled to the aircraft. The altimeter generates vertical position information of the aircraft with respect to the landing approach path. A graphic display disposed within the aircraft concurrently displays a visual representation of the lateral position of the aircraft with respect to the landing approach path and the vertical position of the aircraft with respect to the landing approach path. In so doing, the present invention provides both relative position and altitude of an incoming aircraft with respect to a landing approach path. Thus, the present invention provides a precision equivalent landing system without requiring the equipment and expense associated with ILS or FAA MLS precision landing systems.

Abstract: To reduce error introduced by the local oscillator in the velocity calculations, the receiver has two "tracking channels" and a microcomputer. With numbers required to, simultaneously, lock each of the "tracking channels" each to a respective satellite signal, the microcomputer employs a differential doppler technique to calculate the receiver velocity. The microcomputer calculates a number which represents the difference between the apparent doppler frequency shift of the carrier signal which is transmitted by the first "tracking channel" satellite and which is measured over a specific time period and the apparent doppler frequency shift of the carrier signal which is transmitted by the second "tracking channel" satellite and which is measured over substantially the same time period.

Abstract: Two receiver channels each driven by a common local oscillator signal are employed. The signal developed by the first receiver channel is used to drive in phase (I) and quadrature (Q) counters of a Castas-loop, which phase-locks to the signal. The signal developed by the second receiver channel is used to drive another pair of in phase (I) and quadrature (Q) counters, which develop signals from which heading information is calculated.

Abstract: The present invention provides programmable, remote and automatic numeric control and calibration of analog signal measuring and generating apparatus. Digital values for control signals for control of gain, sensitivity, frequency and the like and for calibration are stored and may be easily modified to follow complex control and calibration functions. Conventional controls are replaced by pushbuttons which initiate calculation of digital control signals for controlling the transfer function of variable elements of the apparatus. Conventional meters and dials are replaced by digital readout devices for indicating operational parameters such as amplitudes, sensitivities, frequencies and the like. Digital values for calibration factors and parameter control settings also may be recorded on suitable recording media for use under recurring conditions and environments.

Abstract: The present invention provides programmable, remote and automatic numeric control and calibration of analog signal measuring and generating apparatus. Digital values for control signals for control of gain, sensitivity, frequency and the like and for calibration are stored and may be easily modified to follow complex control and calibration functions. Conventional controls are replaced by pushbuttons which initiate calculation of digital control signals from controlling the transfer function of variable elements of the apparatus. Conventional meters and dials are replaced by digital readout devices for indicating operational parameters such as amplitudes, sensitivities, frequencies and the like. Digital values for calibration factors and parameter control settings also may be recorded on suitable recording media for use under recurring conditions and environments.