Abstract: A processing function to monitor a horizontal delay gradient in satellite signals is provided. The processing function includes a satellite differencing module, a double differencing module, and a gradient estimator module. The satellite differencing module receives carrier phase measurements for at least two satellites from at least two reference receivers that have a known geometric relationship to each other. The satellites include a monitored satellite and at least one other satellite. The satellite differencing module determines differences in the carrier phase measurements between signals from the monitored satellite and at least one other satellite. The double differencing module forms double-differences between pairs of the at least two reference receivers; compensates the double-differences between the pairs for the known difference-in-position of the reference receivers; and averages the double differences.

Abstract: A processing function to monitor a horizontal delay gradient in satellite signals is provided. The processing function includes a satellite differencing module, a double differencing module, and a gradient estimator module. The satellite differencing module receives carrier phase measurements for at least two satellites from at least two reference receivers that have a known geometric relationship to each other. The satellites include a monitored satellite and at least one other satellite. The satellite differencing module determines differences in the carrier phase measurements between signals from the monitored satellite and at least one other satellite. The double differencing module forms double-differences between pairs of the at least two reference receivers; compensates the double-differences between the pairs for the known difference-in-position of the reference receivers; and averages the double differences.

Abstract: A method for monitoring radio frequency interference (RFI) in a pass band of a satellite signal is provided. The satellite signal includes a carrier signal tracked by a carrier tracking loop located at a receiver. The method involves calculating a statistical variance estimate based on a plurality of discriminator values formed in the carrier tracking loop and calculating an RFI detector from the statistical variance estimate. The method is particularly useful for detecting continuous wave (CW) and narrowband RF interfering signals in the tracking loop pass band.

Abstract: A system is provided for detecting a low-power error condition in a local area augmentation system (LAAS). The system receives a radio signal from a global positioning system (GPS) satellite and measures the wide band and narrow band power of the radio signal in real time. The system estimates the signal-to-noise ratio of the signal in real time based on average wide band and narrow band power measurements. A low signal-to-noise ratio indicates a low power condition. The system then calculates an error contribution due to the low power condition and sums the error contribution with other error contributions to determine the total error in a navigational measurement. To ensure error overbounding, the system may subtract a confidence offset from the signal-to-noise ratio to obtain a lower confidence limit.

Abstract: A 1-sigma pseudorange ground monitor (sigma monitor) is described. The sigma monitor calculates a weighted sum of squared deviations referred to as the discriminator for one or several reference receiver for a specific time period. The sigma monitor also calculates an alert threshold based on the chi-square or near chi-square probability distributions for one or several reference receivers and for the specific time period. The sigma monitor then compares the discriminator with the alert or alarm threshold. If the discriminator is greater than the alert or alarm threshold, an alert or alarm is issued and logged.

Abstract: An apparatus for the detection of positioning system satellite signal distortions includes a correlator that determines a plurality of correlation measurements at points along a correlation curve. The correlation measurements are based upon a correlation between a received satellite signal and a reference. A signal distortion detector determines differences between the correlation measurements along the correlation curve and detects a signal distortion from the differences.

Abstract: A method and system pertaining to a dual antenna compensation algorithm is provided. A local area augmentation system may include a dual antenna system to receive signals from satellites. The system may switch between the antennas to receive signals, and the transition between the antennas should be seamless. Thus, phase variations between the antennas can be determined to correct for code phase variations, and hardware delays between the antennas can be determined to correct for delay differences in signals received from both antennas.

Abstract: A signal deformation monitor that corrects for bias caused by receiver front end signal deformation is disclosed. The signal deformation monitor includes a correlator that determines a plurality of correlation measurements along a correlation curve. The correlation measurements are transformed by a correlation transformation. The correlation transformation subtracts the mean of the correlation measurements over all tracked satellites from each of the correlation measurements calculated by the correlator. The transformed correlation measurements are independent of the front end signal deformation, resulting in a deformation monitor that will more accurately detect satellite signal deformation.

Abstract: A signal deformation monitor that corrects for bias caused by receiver front end signal deformation is disclosed. The signal deformation monitor includes a correlator that determines a plurality of correlation measurements along a correlation curve. The correlation measurements are transformed by a correlation transformation. The correlation transformation subtracts the mean over all tracked satellites from each of the correlation measurements calculated by the correlator. The transformed correlation measurements are independent of the front end signal deformation, resulting in a signal deformation monitor that will more accurately detect satellite signal deformation.

Abstract: Global positioning systems (GPSs) estimate positions of vehicles based on signals from earth-orbiting satellite transmitters. For accuracy and reliability reasons, these systems have traditionally not be used for critical phases of aircraft navigation and guidance, such as aircraft landings. However, recent years have seen the development of ground-augmented GPS systems for use in automatic landing systems. These augmented systems rely on broadcast correction data to correct positions estimates, or solutions, and thus provide more accurate position solutions. Unfortunately, the conventional methods of measuring accuracy in these augmented systems cannot adequately cope with loss of correction data or satellite signals and thus lead to more aborted landings than acceptable. Accordingly, the inventor devised a ground-augmented GPS system that incorporates a better method for determining the accuracy of its position solution.

Abstract: A system is provided for detecting a low-power error condition in a local area augmentation system (LAAS). The system receives a radio signal from a global positioning system (GPS) satellite and measures the wide band and narrow band power of the radio signal in real time. The system estimates the signal-to-noise ratio of the signal in real time based on average wide band and narrow band power measurements. A low signal-to-noise ratio indicates a low power condition. The system then calculates an error contribution due to the low power condition and sums the error contribution with other error contributions to determine the total error in a navigational measurement. To ensure error overbounding, the system may subtract a confidence offset from the signal-to-noise ratio to obtain a lower confidence limit.

Abstract: A method for monitoring radio frequency interference (RFI) in a pass band of a satellite signal is provided. The satellite signal includes a carrier signal tracked by a carrier tracking loop located at a receiver. The method involves calculating a statistical variance estimate based on a plurality of discriminator values formed in the carrier tracking loop and calculating an RFI detector from the statistical variance estimate. The method is particularly useful for detecting continuous wave (CW) and narrowband RF interfering signals in the tracking loop pass band.

Abstract: A method and system pertaining to a dual antenna compensation algorithm is provided. A local area augmentation system may include a dual antenna system to receive signals from satellites. The system may switch between the antennas to receive signals, and the transition between the antennas should be seamless. Thus, phase variations between the antennas can be determined to correct for code phase variations, and hardware delays between the antennas can be determined to correct for delay differences in signals received from both antennas.

Abstract: A global positioning system for use with a plurality of transmitting satellites is disclosed wherein a full position solution is obtained from a number N of satellite transmissions and a plurality of sub-solutions each based on a different number (N−1) of satellite transmissions are obtained to determine if a satellite is faulty. A plurality of sub-sub-solutions is then obtained based on a different combination of N−2 satellites with each combination containing the satellites of different sub-solutions and excluding one other satellite in addition. An examination of the sub-sub-solutions provides an indication of which one of the satellites is the failed satellite.

Abstract: A global positioning system for use with a plurality of transmitting satellites is disclosed wherein a full position solution is obtained from a number N of satellite transmissions and a plurality of sub-solutions each based on a different number (N−1) of satellite transmissions are obtained to determine if a satellite is faulty. A plurality of sub-sub-solutions is then obtained based on a different combination of N−2 satellites with each combination containing the satellites of different sub-solutions and excluding one other satellite in addition. An examination of the sub-sub-solutions provides an indication of which one of the satellites is the failed satellite.

Abstract: Global positioning systems (GPSs) estimate positions of vehicles based on signals from earth-orbiting satellite transmitters. For accuracy and reliability reasons, these systems have traditionally not be used for critical phases of aircraft navigation and guidance, such as aircraft landings. However, recent years have seen the development of ground-augmented GPS systems for use in automatic landing systems. These augmented systems rely on broadcast correction data to correct positions estimates, or solutions, and thus provide more accurate position solutions. Unfortunately, the conventional methods of measuring accuracy in these augmented systems cannot adequately cope with loss of correction data or satellite signals and thus lead to more aborted landings than acceptable. Accordingly, the inventor devised a ground-augmented GPS system that incorporates a better method for determining the accuracy of its position solution.

Abstract: A system to determine, from inertial reference apparatus and from GPS receiver apparatus, acceleration signals along a predetermined axis to determine the failure of a GPS satellite signal by comparison of the acceleration signals and to monitor newly acquired GPS satellite signals to determine if a satellite drift was present prior to acquisition.

Abstract: A system to determine when a GPS satellite signal has begun to drift prior to acquisition by producing a discriminator which is used to determine the satellite error bound and the satellite error bound is used to determine the drift error bound indicative of an existing drift in the satellite.

Abstract: A navigation system, incorporating a unique method for detecting failures and determining an accuracy or error bound, has a receiver for receiving signals from several remote transmitters and a processor for determining a position solution from the signals. The processor, preferably employing Kalman filtering techniques, also determines several position subsolutions from subsets of the signals. The processor then computes covariance-based solution separation parameters based on statistical worst-case differences, or separations, between the position solution and the subsolutions. Similarly, the processor also computes error parameters defining statistical worst-case errors in each position subsolution. With the solution separation and the subsolution error parameters, the processor determines an error bound for the position solution. The processor also uses the separation parameters as detection thresholds for detecting transmitter failures.

Abstract: A differential satellite positioning system is configured to include a plurality of satellite positioning system receivers in spatial proximity of one another for determining independent pseudo range values which are processed in accordance with a selected averaging scheme for determining highly reliable satellite differential corrections.