Ground-based system and method to extend the detection of excessive delay gradients using parity corrections
First Claim
1. A processing module to monitor a horizontal delay gradient in satellite signals representative of an ionospheric delay gradient, the processing function comprising:
- a satellite differencing module configured to receive carrier phase measurements for at least two satellites from at least three reference receivers, the at least two satellites including a monitored satellite and at least one other satellite, wherein the at least three reference receivers have a known geometric relationship to each other, and wherein the satellite differencing module determines differences in the carrier phase measurements between signals from the monitored satellite and at least one of the at least one other satellite;
a double differencing module configured to;
form double-differences between one or more pairs of the at least three reference receivers based on the differences in the carrier phase measurements,compensate the double-differences between the pairs for the known difference-in-position of the reference receivers in the pairs,perform a modulo operation to limit the compensated double-differences to a range of minus one-half wavelength to plus one-half wavelength, andfor the monitored satellite, average the double differences over the other satellites among the at least two satellites; and
a parity test module configured to input the averaged compensated double differences when the average of the compensated double differences over the other satellites among the at least two satellites exceed a parity enable threshold; and
a gradient estimator module configured to estimate a magnitude of the horizontal delay gradient based on a set of the averaged compensated double-differences input from the parity test module.
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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, a parity test module, and a gradient estimator module. The satellite differencing module receives carrier phase measurements for at least two satellites from at least three reference receivers. The satellite differencing module determines differences in the carrier phase measurements between signals from the monitored satellite and at least one of the at least one other satellite. The double differencing module: forms double-differences between pairs of the reference receivers; compensates the double-differences between the pairs; performs a modulo operation; and averages the double differences. The parity test module inputs the averaged compensated double differences when the average exceeds a parity enable threshold. The gradient estimator module configured is to estimate a magnitude of the horizontal delay gradient.
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Citations
20 Claims
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1. A processing module to monitor a horizontal delay gradient in satellite signals representative of an ionospheric delay gradient, the processing function comprising:
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a satellite differencing module configured to receive carrier phase measurements for at least two satellites from at least three reference receivers, the at least two satellites including a monitored satellite and at least one other satellite, wherein the at least three reference receivers have a known geometric relationship to each other, and wherein the satellite differencing module determines differences in the carrier phase measurements between signals from the monitored satellite and at least one of the at least one other satellite; a double differencing module configured to; form double-differences between one or more pairs of the at least three reference receivers based on the differences in the carrier phase measurements, compensate the double-differences between the pairs for the known difference-in-position of the reference receivers in the pairs, perform a modulo operation to limit the compensated double-differences to a range of minus one-half wavelength to plus one-half wavelength, and for the monitored satellite, average the double differences over the other satellites among the at least two satellites; and a parity test module configured to input the averaged compensated double differences when the average of the compensated double differences over the other satellites among the at least two satellites exceed a parity enable threshold; and a gradient estimator module configured to estimate a magnitude of the horizontal delay gradient based on a set of the averaged compensated double-differences input from the parity test module. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of monitoring for a delay gradient to a monitored satellite representative of an ionospheric delay gradient, the method comprising:
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receiving carrier phase measurements from at least three reference receivers, wherein the at least three reference receivers substantially simultaneously receive radio frequency signals from the monitored satellite and at least one other satellite, and wherein the at least three reference receivers have a known geometric relationship to each other; determining differences in the carrier phase measurements between the signals from the monitored satellite and at least one other satellite for the at least three reference receivers; forming double-differences between pairs of the at least three reference receivers; compensating the double-differences for the known difference-in-position of the reference receivers in the pairs; performing a modulo operation on the compensated double-differences to limit the compensated double-differences to a range of minus one-half wavelength to plus one-half wavelength; averaging the compensated double differences over the at least one other satellites; directing the averaged compensated double differences to a parity test module when the averaged compensated double differences exceed a parity enable threshold; outputting a set of the averaged compensated double-differences input from the parity test module to a gradient estimator module; and estimating a magnitude of a horizontal delay gradient based on the set of averaged compensated double-differences. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14)
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15. A ground based system to monitor for a horizontal delay gradient to a monitored satellite representative of an ionospheric delay gradient, the system comprising:
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at least three reference receivers configured to substantially simultaneously receive radio frequency signals from the monitored satellite and at least one other satellite, wherein the at least three reference receivers have a known geometric relationship to each other; and a processing function communicatively coupled to the at least three reference receivers, the processing function configured to; receive carrier phase measurements for the monitored satellite and at least one other satellite from the at least three reference receivers, determine differences in the carrier phase measurements between the signals transmitted from the monitored satellite and at least one other satellite and substantially simultaneously received at the at least three reference receivers, form double-differences between pairs of the at least three reference receivers based on the differences in the carrier phase measurements, compensate the double-differences for the known difference-in-position of the reference receivers in the pairs, perform a modulo operation to limit the compensated double-differences to a range of minus one-half wavelength to plus one-half wavelength, average the compensated double-differences over the other satellites for the monitored satellite at the pairs, and input the averaged compensated double differences at a parity test module when the average of the compensated double differences exceed a parity enable threshold; estimate a magnitude of the horizontal delay gradient based on a set of the averaged compensated double-differences input from the parity test module. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification