Aspects of the present disclosure may improve the accuracy of the known azimuth determination techniques by employing more than two GNSS antennas positioned on a base station antenna. Techniques may use one or more combinations of the GNSS antennas to determine an azimuth of the base station antenna, which serve to improve accuracy of an azimuth determination.

Disclosed is a method and apparatus for correcting a satellite image acquisition time. The method may include receiving, from a ground-based orbit propagator, an initially predicted imaging time, a correction command execution time, and a desired satellite position for imaging, and calculating a waiting time for imaging, a predicted satellite position, a correction time, and a corrected imaging time to correct a satellite image acquisition time.

Examples for enhancing sensitivity to reflected GNSS signals are presented herein. An example may involve identifying, by a receiver, a particular positioning signal that reflected off a reflecting plane prior to reaching the receiver. The receiver may be in motion. The example may also involve determining a reflected satellite position for a satellite that transmitted the particular positioning signal based on identifying the particular positioning signal. The reflected satellite position may be determined by reflecting a position of the satellite about the reflecting plane. The example may also involve determining a direction vector to the reflected satellite position for the satellite and performing coherent integration over a threshold duration of time to increase a signal to noise ratio for the particular positioning signal based on the direction vector to the reflected satellite position.

A global navigation satellite system (GNSS) receiver includes: at least one radio frequency (RF) front end configured to receive a GNSS signal from a single GNSS antenna and to digitize the GNSS signal into a digitized GNSS signal; at least one processor configured to: calculate weight to be applied to a sample of a block of samples of the digitized GNSS signal; apply the weight to at least one sample of the block of samples of the digitized GNSS signal to create a weighted GNSS signal; and perform signal processing on the weighted GNSS signal.

The present disclosure is directed to utilities (methods, systems, apparatuses) associated with improving the signal-to-noise ratio of a wireless signal at a receiver. It is known in the art to correlate a received signal with a replica signal generated at the receiver to improve reception. However, the inventors have determined that correlation using a replica signal which is not completely accurate may be detrimental. An improved method of correlation disclosed herein includes identifying data bits which are predictable and performing correlation with respect to those data bits while ignoring data bits which are identified as unpredictable. This method may have particular advantages in the case of receivers having attenuated reception (e.g., indoors) after losing a data connection used for receipt of assistance data.

A system to detect spoofing attacks is provided. The system includes a satellite-motion-and-receiver-clock-correction module, a compute-predicted-range-and-delta-range module, a subtractor, and delta-range-difference-detection logic. The satellite-motion-and-receiver-clock-correction module periodically inputs, from a global navigation satellite system (GNSS) receiver, a carrier phase range for a plurality of satellites. The satellite-motion-and-receiver-clock-correction module outputs a corrected-delta-carrier-phase range for a current epoch to a first input of a subtractor. The compute-predicted-range-and-delta-range module outputs a predicted delta range to a second input of the subtractor. The predicted delta range is based on inertial measurements observed for the current epoch. The subtractor outputs a difference between the corrected-delta-carrier-phase range and the predicted delta range for the current epoch to delta-range-difference-detection logic. The delta-range-difference-detection logic determines if the difference exceeds a selected-range threshold. If the difference exceeds the selected-range threshold, the delta-range-difference-detection logic determines the GNSS receiver was spoofed in the current epoch.

Provided is a positioning system including: a storage apparatus configured to store orbit information indicating the position of a positioning satellite; and a positioning apparatus configured to perform a positioning process based on the orbit information, wherein the positioning apparatus includes an acquisition unit configured to acquire state-related information related to the state of the positioning apparatus, and a transmission unit configured to transmit, to the storage apparatus, the state-related information acquired by the acquisition unit, and the storage apparatus includes a receiving unit configured to receive the state-related information transmitted from the transmission unit, and an adjustment unit configured to adjust the content of the orbit information to be transmitted to the positioning apparatus, based on the state-related information received by the receiving unit.

Snapshot receiver that comprises a correlator module for correlating incoming GNSS signals and a transform module that transforms resulting correlated outputs using a Fractional Fourier Transform (FrFT) process, to thereby compensate for weak and dynamic signals. The output of the transform module is an estimated Doppler rate with high accuracy. The estimated Doppler rate is passed to a super-resolution-measurement (SRM) module, which outputs error values of the estimated Doppler rate and a pseudorange (measured distance-to-satellite) via a phase dead reckoning (DR) calculation for the snapshot receiver. The pseudorange and error values are passed to a navigator module that determines position information based on those inputs. In some embodiments, the SRM module comprises a maximum likelihood estimator (MLE).

A railway positioning method, based on the movement of a train determined by a signal receiver of a satellite navigation system embedded onboard the train, and on the movement of the train determined by an odometer embedded onboard the train, and a map of the railway tracks, by determination of the ionospheric propagation bias corresponding to a propagation bias of the signal carrier phase of the satellite navigation system, comprises the steps of, by line of sight of the satellites of the navigation system: estimating the biased ionospheric drift by difference between an integrated Doppler term determined by the receiver and a biased estimation of the movement of the train by the odometer; estimating the odometer drift bias and the drift bias of the local clock of the receiver, by least squares resolution of the speed determined by the satellite navigation system, of the drift bias of the local clock of the receiver, and of the odometer drift bias; correcting the estimation of the ionospheric drift, by subtraction of the estimated odometer drift bias; and correcting the integrated Doppler term using the drift bias of the local clock of the receiver and the ionospheric drift bias, and correcting the pseudo-distance deviations using the ionospheric drift bias.

A satellite-based positioning system (SPS) signal processing technique re-samples a received series of PRN sequences from an SPS satellite to align them with a nominal sampling rate for a corresponding series of perfect reference PRN replica sequences.