Abstract: The present invention includes a method for a combined use of a local positioning system, a local RTK system and a regional, wide-area, or global differential carrier-phase positioning system (WADGPS) in which disadvantages associated with the local positioning system, the RTK and the WADGPS navigation techniques when used separately are avoided. The method includes determining a first position of the object based on information from the WADGPS, and determining a second position of the object based on position information from a local positioning/RTK positioning system. Thereafter, position determined by the WADGPS and the position determined by the local positioning/RTK positioning system are compared.

Abstract: A new three-frequency technique for obtaining geometry free, refraction-corrected, ambiguity-resolved, carrier-phase measurements has been described. First, the ambiguities on at least two wide-lane carrier-phase measurement differences are obtained by averaging the corresponding frequency weighted code measurements. These two ambiguity-resolved measurements are then combined into a composite refraction-corrected measurement. The resulting composite measurement is quite noisy due to the amplification of the multipath noise in the original carrier-phase measurements. But this noisy refraction-corrected carrier-phase measurement can be smoothed with another minimum-noise, refraction-corrected carrier-phase composite measurement. The minimum-noise, refraction-corrected composite measurement is constructed from the primary carrier-phase measurements prior to resolving their whole-cycle ambiguities.

Abstract: A method and system are provided to determine a relative position vector between primary receiver associated with a reference station and secondary receiver associated with a user. The method and system determine a position of the reference station at the reference station according to signals received thereat from a plurality of satellites, determine a position of the user receiver at the user based on measurements obtained thereat and on error corrections computed at the reference station, and compute the relative position vector by differencing the position of the reference station and the position of the user.

Abstract: The present invention includes a process for navigating an object according to signals from satellites by propagating the position of the object forward in time using successive changes in the carrier-phase measurements. The process computes at a low rate matrices required for solving for the position of the objects, and repeatedly uses the most recently computed matrices to compute position updates at a high rate until the next low-rate computation is completed.

Abstract: The present invention includes a method for a combined use of a local RTK system and a regional, wide-area, or global differential carrier-phase positioning system (WADGPS) in which disadvantages associated with the RTK and the WADGPS navigation techniques when used separately are avoided. The method includes using a known position of a user receiver that has been stationary or using an RTK system to initialize the floating ambiguity values in the WADGPS system when the user receiver is moving. Thereafter, the refraction-corrected carrier-phase measurements obtained at the user GPS receiver are adjusted by including the corresponding initial floating ambiguity values and the floating ambiguity values are treated as well known (small variance) in subsequent processes to position the user receiver in the WADGPS system.

Abstract: A method for generating satellite clock corrections for a WADGPS network computers satellite clock corrections after removing other substantial error components. Errors caused by the ionosphere refraction effects are removed from GPS measurements taken at reference stations using dual-frequency GPS measurements. The multipath noise are removed by smoothing of GPS pseudorange code measurements with carrier-phase measurements. The tropospheric refraction effect can be largely removed by modeling, and if desired, can be improved by the use of small stochastic adjustments included in the computation of the clock correction. After removing the above error factors, satellite clock corrections are computed for individual reference stations, and an average clock correction is formed for each of a plurality of satellites by taking an average or weighted average of the satellite clock corrections over reference stations to which the satellite is visible.

Abstract: The present invention includes a method for a combined use of a local RTK system and a regional, wide-area, or global differential carrier-phase positioning system (WADGPS) in which disadvantages associated with the RTK and the WADGPS navigation techniques when used separately are avoided. The method includes determining a floating ambiguity value and a first position of an object using WADGPS in a first mode of operation, and determining a second position of the object using the local RTK system in a second mode of operation.

Abstract: A method for generating an ambiguity-resolved, refraction-corrected, and noise-minimized carrier-phase measurement. The method includes forming a first composite measurement using GPS carrier-phase measurements on the L1, L2 and L5 frequencies. To reduce the noise in the first composite measurement, the method further includes forming a second composite measurement using GPS carrier-phase measurements on at least two of the three GPS carrier frequencies. The second composite measurement is formed to have a small multi-path noise therein so that it can be used to smooth the first composite measurement so that the multipath noise is minimized.

Abstract: A method for detecting and identifying a faulty measurement among a plurality of GPS measurements, obtained by a GPS receiver with respect to a plurality of satellites in view of the GPS receiver, determines whether the plurality of GPS measurements include a faulty measurement. In response to a determination that the plurality of GPS measurements include a faulty measurement, the method identifies a satellite contributing the faulty measurement by computing a correlation value associated with each of the plurality of satellites, and selecting a satellite associated with a highest correlation value as the satellite contributing the faulty measurement.

Abstract: A method of fast GPS carrier phase integer ambiguity resolution is based on properties of a Residual Sensitivity Matrix (S matrix), which directly relates a set of integer ambiguities to carrier phase residuals. In one embodiment, the method uses the singular value decomposition of the S Matrix to split the integer ambiguity set into two integer ambiguity subsets and to derive a relationship between the two integer ambiguity subsets. Thus, searching for the integer ambiguity set is reduced to searching for one of the two integer ambiguity subsets, resulting in greatly reduced search space. In an alternative embodiment, a portion of the rows of the S matrix that are linearly independent rows are selected and the S matrix is rearranged according to the selection. The rearranged S matrix is then split into four sub-matrices, which are used to relate the two integer ambiguity subsets.

Abstract: A Global Positioning System receiver includes an intermediate frequency (IF) processor configured to downconvert broadcast signal to generate a first channel signal which is further downconverted to recover a PRN signal by an angle rotator. The receiver further includes a signal generator configured to generate N gated PRN signals. The N gated PRN signals are generated based on a local replica PRN signal time-divided by M intervals within a chip period of the local replica PRN signal. N and M are positive integers. A number of correlators is also provided. Each of which the correlators are configured to multiply a respective one of N gated PRN signals with the PRN signal to generate a number of correlation values. The correlation values are utilized to monitor distortions in the broadcast signal and/or to track the carrier frequency signal. Further, a corresponding method is also provided.

Abstract: A Global Positioning System receiver includes an intermediate frequency (IF) processor configured to downconvert broadcast signal to generate a first channel signal which is further downconverted to recover a PRN signal by an angle rotator. The receiver further includes a signal generator configured to generate N gated PRN signals. The N gated PRN signals are generated based on a local replica PRN signal time-divided by M intervals within a chip period of the local replica PRN signal. N and M are positive integers. A number of correlators is also provided. Each of which the correlators are configured to multiply a respective one of N gated PRN signals with the PRN signal to generate a number of correlation values. The correlation values are utilized to monitor distortions in the broadcast signal and/or to track the PRN signal with the local replica PRN signal. Further, methods of monitoring and/or tracking the PRN signal with the local replica PRN signal by utilizing the correlation values are also provided.

Abstract: An improved method and apparatus for effecting code synchronization in a global positioning system receiver is disclosed herein. Within the receiver, digital in-phase (I) and quadrature (Q) samples of a plurality of received pseudorandom noise (PRN) encoded signals are provided to a code synchronization circuit. The code synchronization circuit is designed for coherent-mode operation when the receiver has achieved phase-lock with one of the PRN encoded signals, and operates in a non-coherent mode otherwise.The code synchronization circuit includes an I-channel correlator for producing a coherent-mode discrimination signal by correlating in-phase (I) samples of a first of said PRN encoded signals with a discrimination pattern, wherein the first PRN encoded signal is encoded with a first PRN code.

Abstract: An improved method and apparatus for effecting code synchronization in a global positioning system receiver is disclosed herein. Within the receiver, digital in-phase (I) and quadrature (Q) samples of a plurality of received pseudorandom noise (PRN) encoded signals are provided to a code synchronization circuit. The code synchronization circuit is designed for coherent-mode operation when the receiver has achieved phase-lock with one of the PRN encoded signals, and operates in a non-coherent mode otherwise.The code synchronization circuit includes an I-channel correlator for producing a coherent-mode discrimination signal by correlating in-phase (I) samples of a first of said PRN encoded signals with a discrimination pattern, wherein the first PRN encoded signal is encoded with a first PRN code.

Abstract: A traffic signal preemption system, and a related method for its use, using differential global positioning system (GPS) measurements for accurate monitoring of the position, speed and direction of an emergency or service vehicle approaching a controlled intersection. The preemption system includes a reference GPS receiver, for computing GPS measurement corrections, and a GPS receiver in each vehicle, which transmits its GPS measurements by radio to a receiver located at the controlled intersection. A computer also located at the intersection uses corrected vehicle position, speed and direction measurements, in conjunction with previously recorded data defining approach routes to the intersection, to determine the optimum time to switch a traffic light controller to preemption mode to permit safe passage of the vehicle. GPS measurement corrections may be applied in a vehicle computer or in the computer located at the intersection.

Abstract: In a DGPS, accurate post-processed corrections to user receiver locations are made while minimizing the amount of data required to be stored at reference station and user receiver positions. Further, such corrections are available even if reference station corrections cannot be received by the user in real-time. The user receiver acquires in-view GPS satellites, computes, and stores user stand-alone position, time of computation, and acquired satellite identification. Reference stations generate correction data for the same satellites at the same time period, which correction data are broadcast but need not be received by the user in real-time. Almanac information for the relevant satellites is also made available to at least the user receiver. Stand-alone user receiver positional data and the almanac data for the same acquired satellites are used by a CPU, located at a remote site able to receive reference station transmissions and/or in the user receiver, to compute corrections to user receiver positions.

Abstract: A method and apparatus for synthesizing a stable reference signal of a desired frequency within a spread spectrum receiver is disclosed herein. The spread spectrum receiver is designed for use in conjunction with a global positioning system (GPS) receiver, and operates to receive broadcast differential GPS correction information. The present frequency synthesis technique contemplates generating a sequence of timing signals within the GPS receiver on the basis of GPS satellite signals received thereby, and providing the timing signals to the signal receiver. Within the signal receiver, the signal cycles of a local oscillator occurring between ones of the timing signals are counted. The frequency of the local oscillator is then determined by dividing the counted cycles of the local oscillator by one of the known time intervals. The determined frequency of output signals produced by the local oscillator is then scaled so as necessary to produce the reference signal of desired frequency.

Abstract: A technique for smoothing pseudorange code measurements made in a global positioning system (GPS) receiver, with carrier phase measurements, over an extended time interval but without distortion that usually results from a divergence between code-derived pseudorange measurements and carrier-derived measurements. The basic principle of the invention is to remove ionospheric effects and Doppler effects from the pseudorange code measurements prior to filtering over an extended time interval. Removal of ionospheric effects may be effected by applying corrections received from a reference receiver, or may be accomplished using measured or modeled ionospheric data available to the receiver. The invention is applicable to differential GPS position finding using remote receivers having only a single-frequency capability, but is also applicable to stand-alone GPS receivers of any type.

Abstract: A technique using pseudo-satellites, or "pseudolites," for resolving whole-cycle ambiguity that is inherent in phase-angle measurments of signals received from multiple satellite-based transmitters in a global positioning system. The relative position of a secondary receiving antenna with respect to a reference antenna is approximately known or approximately initially determined and then measurements from a minimum number of satellites are used to determine an initial set of potential solutions to the relative position of the secondary antenna that fall within a region of uncertainty surrounding the approximate position. Redundant measurements are taken from one or more pseudolites, and used to progressively reduce the number of potential solutions to close to one.

Abstract: A technique for resolving whole-cycle ambiguity that is inherent in phase-angle measurements of signals received from multiple satellite-based transmitters in a global positioning system. The relative position of a secondary receiving antenna with respect to a reference antenna is approximately known or approximately initially determined and then measurements from a minimum number of satellites are used to determine an initial set of potential solutions to the relative position of the secondary antenna that fall within a region of uncertainty surrounding the approximate position. Redundant measurements are taken from one or more additional satellites and used to progressively reduce the number of potential solutions to close to one. Even if the number of potential solutions is not reduced to one true solution, the number can be further reduced by using additional measurements taken at different time intervals, at which different satellite geometries prevail.