US 8,525,727 B2 · Position and velocity uncertainty metrics in GNSS receivers

Abstract

A GNSS navigation system and navigation method for determining user position, user velocity, and improved uncertainty metrics for position and velocity. A measurement engine in an applications processor of the system determines pseudorange and delta range values over each time period for each received satellite signal, and also determines measurement noise variances for both pseudorange and delta range for the individual signals. The satellite-specific pseudorange and delta range measurement variances are used to determine the position and velocity uncertainties by a position engine, either by way of a least-squares linearization or by way of an enhanced Kalman filter. The uncertainties may be communicated to the system user, or used in generating an integrated position and velocity result from both the GNSS navigation function and an inertial navigation system result.

Claims36

Dependent claims

A navigation system, comprising:

an antenna;
and
Global Navigation Satellite System (GNSS) receiver circuitry coupled to the antenna for receiving GNSS signals from a plurality of satellites, and comprising:
a measurement engine for determining, from each of the received GNSS signals, a pseudorange value and a pseudorange variance, the measurement engine comprising:
a digital measurement engine channel for determining the pseudorange value and pseudorange variance for an associated one of the GNSS signals, comprising:
code generator circuitry, for generating a replica code at a plurality of delay times;
a delay-locked loop for measuring correlation between the associated GNSS signal and the replica code at a selected code-phase relationship, comprising a plurality of correlators, each for correlating the associated GNSS signal with the replica code at an associated delay time, the plurality of correlators including at least an early correlator and a late correlator;
and
a delay-locked loop discriminator having inputs coupled to the plurality of correlators, for generating an error signal responsive to a difference in the correlations by the early and late correlators;
a filter for generating a discriminator output signal responsive to the error signal and
circuitry for calculating the pseudorange value from the measured correlations for each GNSS signal, and for calculating the pseudorange variance for each GNSS signal from a variance of the discriminator signal output signal the measured correlations over time.

8 more elements

A method of determining position based on signals transmitted by satellites in a GNSS system, comprising:

receiving signals from a plurality of satellites over a plurality of time intervals, the received signals comprising encoded information indicative of a time of transmission from each satellite;
for each of the received satellite signals, for each of the time intervals, determining a pseudorange value and a pseudorange variance for each of the received satellite signals, by performing a sequence of operations comprising:
correlating a replica code with the satellite signal at a plurality of delay times to produce a plurality of correlation results;
determining a delay time error value responsive to the values of the plurality of correlation results;
adjusting the delay times of the correlating step responsive to the delay time error value;
repeating the correlating, determining, and adjusting steps;
calculating the pseudorange value from the correlation results;
and
calculating the pseudorange variance from a variance of the delay time error values over time;
and
for each of the time intervals, determining position and position uncertainty values from the pseudorange values and the pseudorange variances.

8 more elements

A navigation system, comprising:

an antenna;
and
Global Navigation Satellite System (GNSS) receiver circuitry coupled to the antenna for receiving GNSS signals from a plurality of satellites, and comprising:
a measurement engine for determining, from each of the received GNSS signals, a pseudorange value, a delta range value, a pseudorange variance, and a delta range variance for each time interval over a sequence of time intervals;
and
a position engine, coupled to the measurement engine and constructed from programmable logic circuitry, for determining from the pseudorange values, delta range values, pseudorange variances, and delta range variances, a position and a velocity of the navigation system, and uncertainty values for the determined position and velocity, for each of the time intervals by applying the pseudorange values, delta range values, pseudorange variances, and delta range variances for each time interval to a Kalman filter;
further comprising:
program memory, coupled to the programmable logic circuitry of the position engine, for storing executable program instructions that, when executed by the programmable logic circuitry, cause the position engine to perform a plurality of operations in an iterative fashion, each iteration corresponding to a time interval, each iteration comprising the operations of:
generating estimates of a state vector and a covariance by a plurality of operations comprising:
calculating a predicted a priori state vector estimate for the current iteration based on an a posteriori state vector estimate from a previous iteration, the state vector estimates including parameters indicating a position, a clock bias value, a velocity, and a clock drift value;
calculating a predicted a priori covariance for the current iteration based on an a posteriori covariance estimate from the previous iteration and a process noise covariance;
calculating a gain matrix based on a measurement noise covariance corresponding to pseudorange and delta range variances for the GNSS signals in the current time interval;
calculating an a posteriori state vector estimate for the current iteration based on the pseudorange and delta range values for the GNSS signals in the current time interval, on the gain matrix, and on the predicted a priori state vector estimate for the current iteration;
and
calculating an a posteriori covariance for the current iteration based on the a priori covariance and on the gain matrix;
generating dynamic estimates of a state vector and a covariance by a plurality of operations comprising:
dynamically estimating the process noise covariance;
calculating a dynamic predicted a priori covariance for the current iteration based on a dynamic a posteriori covariance estimate from the previous iteration and on the dynamic estimate of the process noise covariance;
calculating a dynamic gain matrix based on a measurement noise covariance corresponding to pseudorange and delta range variances for the GNSS signals in the current time interval and on the dynamic predicted a priori covariance;
and
calculating a dynamic a posteriori covariance for the current iteration based on the dynamic predicted a priori covariance and on the dynamic gain matrix;
generating a current position and a current velocity of the navigation system from the a posteriori state vector estimate;
generating position and velocity uncertainty values based on the a posteriori covariance and the dynamic a posteriori covariance.

20 more elements

A navigation system, comprising:

an antenna;
and
Global Navigation Satellite System (GNSS) receiver circuitry coupled to the antenna for receiving GNSS signals from a plurality of satellites, and comprising:
a measurement engine for determining, from each of the received GNSS signals, a pseudorange value, a delta range value, a pseudorange variance, and a delta range variance for each time interval over a sequence of time intervals, the measurement engine comprising:
a plurality of digital measurement engine channels, each digital measurement engine channel for determining the pseudorange value, delta range value, pseudorange variance, and delta range variance for one of the GNSS signals, each of the digital measurement engine channels comprising:
a delay-locked loop for measuring a correlation between an associated GNSS signal and a replica code at a selected code-phase relationship;
delay-locked loop discriminator circuitry for adjusting the code-phase relationship used by the delay-locked loop responsive to the measured correlation;
a frequency-locked loop for measuring a correlation between the associated GNSS signal and a replica code at a selected carrier-phase relationship;
and
frequency-locked loop domain discriminator circuitry for adjusting the carrier-phase relationship used by the frequency-locked loop responsive to the measured correlation;
and
circuitry for calculating the pseudorange values and delta range values from the measured correlations;
and
a position engine, coupled to the measurement engine, for determining from the pseudorange values, delta range values, pseudorange variances, and delta range variances, a position and a velocity of the navigation system, and uncertainty values for the determined position and velocity, for each of the time intervals by applying the pseudorange values, delta range values, pseudorange variances, and delta range variances for each time interval to a Kalman filter;
wherein each digital measurement engine channel measures a correlation peak value;
and wherein the calculating circuitry calculates the pseudorange variance from a variance of measured correlation peak values from a mean correlation peak value.

13 more elements

A method of determining position and velocity based on signals transmitted by satellites in a GNSS system, comprising:

receiving signals from a plurality of satellites over a plurality of time intervals, the received signals comprising encoded information indicative of a time of transmission from each satellite;
for each of the received satellite signals, for each of the time intervals, determining a pseudorange value, a delta range value, a pseudorange variance, and a delta range variance;
and
for each of the time intervals, applying the pseudorange value, the delta range value, the pseudorange variance, and the delta range variance to a Kalman filter to derive the position and velocity, and to derive position and velocity uncertainty values, comprising, for each time interval:
generating estimates of a state vector and a covariance by:
calculating a predicted a priori state vector estimate for the current time interval based on an a posteriori state vector estimate from a previous time interval, the state vector estimates including parameters indicating a position, a clock bias value, a velocity, and a clock drift value;
calculating a predicted a priori covariance for the current time interval based on an a posteriori covariance estimate from the previous time interval and a process noise covariance;
calculating a gain matrix based on a measurement noise covariance corresponding to pseudorange and delta range variances for the GNSS signals in the current time interval;
calculating an a posteriori state vector estimate for the current time interval based on the pseudorange and delta range values for the GNSS signals in the current time interval, on the gain matrix, and on the predicted a priori state vector estimate for the current time interval;
and
calculating an a posteriori covariance for the current time interval based on the a priori covariance and on the gain matrix;
generating dynamic estimates of a state vector and a covariance by:
dynamically estimating the process noise covariance;
calculating a dynamic predicted a priori covariance for the current time interval based on a dynamic a posteriori covariance estimate from the previous time interval and on the dynamic estimate of the process noise covariance;
calculating a dynamic gain matrix based on a measurement noise covariance corresponding to pseudorange and delta range variances for the GNSS signals in the current time interval and on the dynamic predicted a priori covariance;
and
calculating a dynamic a posteriori covariance for the current time interval based on the dynamic predicted a priori covariance and on the dynamic gain matrix;
generating a current position and a current velocity of the navigation system from the a posteriori state vector estimate;
and
generating position and velocity uncertainty values based on the a posteriori covariance and the dynamic a posteriori covariance.

17 more elements

A method of determining position and velocity based on signals transmitted by satellites in a GNSS system, comprising:

receiving signals from a plurality of satellites over a plurality of time intervals, the received signals comprising encoded information indicative of a time of transmission from each satellite;
determining the pseudorange value and the pseudorange variance comprises, for each of the received satellite signals:
correlating a replica code with a satellite signal at a plurality of delay times to produce a plurality of correlation results;
determining a delay time error value responsive to the values of the plurality of correlation results;
adjusting the delay times of the correlating step responsive to the delay time error value;
repeating the correlating, determining, and adjusting steps;
and
calculating the pseudorange value from the correlation results;
determining the delta range value and the delta range variance comprises, for each of the received satellite signals:
correlating a replica code with a satellite signal at a plurality of frequencies to produce a plurality of correlation results;
determining a frequency error value responsive to the values of the plurality of correlation results;
adjusting the frequencies of the correlating step responsive to the frequency error value;
repeating the correlating, determining, and adjusting steps;
and
calculating the delta range value from the correlation results;
for each of the time intervals, applying the pseudorange value, the delta range value, the pseudorange variance, and the delta range variance to a Kalman filter to derive the position and velocity, and to derive position and velocity uncertainty values;
wherein the step of determining the pseudorange value, the delta range value, the pseudorange variance, and the delta range variance further comprises, for each of the received satellite signals:
measuring a correlation peak value for each time interval;
and
calculating the pseudorange variance from a variance of measured correlation peak values from a mean correlation peak value.

17 more elements

Dependencies are inferred from the claim text.

Position and velocity uncertainty metrics in GNSS receivers

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Position and velocity uncertainty metrics in GNSS receivers

Life of this patent

Abstract

Claims36