Package org.orekit.estimation.measurements.filtering

Class SingleFrequencyHatchFilter

  • public class SingleFrequencyHatchFilter
extends Object
    Single frequency Hatch filter.

    The single frequency Hatch Filter is used to smooth the pseudo-range measurement using either a Doppler measurement or a carrier phase measurement.

    Since:
    11.2
    Author:
    Louis Aucouturier
    See Also:
    "Subirana, J. S., Hernandez-Pajares, M., and José Miguel Juan Zornoza. (2013). GNSS Data Processing: Fundamentals and Algorithms. European Space Agency.", "Zhou, Z., and Li, B. (2017). Optimal Doppler-aided smoothing strategy for GNSS navigation. GPS solutions, 21(1), 197-210."

    • Constructor Detail

      • SingleFrequencyHatchFilter

        public SingleFrequencyHatchFilter​(ObservationData initCode,
                                  ObservationData initSmoothing,
                                  MeasurementType type,
                                  double wavelength,
                                  double threshold,
                                  int N,
                                  double integrationTime)
        Constructor for the Single Frequency Hatch Filter.

        The threshold parameter corresponds to the maximum difference between non-smoothed and smoothed pseudo range value, above which the filter is reset.

        Parameters:
        initCode - initial code measurement
        initSmoothing - initial smoothing measurement
        type - type of the smoothing measurement (CARRIER_PHASE or DOPPLER)
        wavelength - measurement value wavelength (m)
        threshold - threshold for loss of lock detection (represents the maximum difference between smoothed and measured values for loss of lock detection)
        N - window size of the Hatch Filter
        integrationTime - time interval between two measurements (s)

    • Method Detail

      • filterData

        public ObservationData filterData​(ObservationData codeData,
                                  ObservationData smoothingData)
        This method filters the provided data given the state of the filter.
        Parameters:
        codeData - input code observation data
        smoothingData - input smoothing observation data
        Returns:
        the smoothed observation data

      • getCodeHistory

        public ArrayList<Double> getCodeHistory()
        Get the history of the pseudo-range values used by the filter.
        Returns:
        the history of the pseudo-range values used by the filter

      • getSmoothedCodeHistory

        public ArrayList<Double> getSmoothedCodeHistory()
        Get the history of the smoothed pseudo-range values used by the filter.
        Returns:
        the smoothedCodeHistory

      • getThreshold

        public double getThreshold()
        Get the threshold for loss of lock detection.

        It represents the maximum difference between smoothed and measured values for loss of lock detection.

        Returns:
        the threshold for loss of lock detection

      • updatePreviousSmoothedCode

        public void updatePreviousSmoothedCode​(double smoothedCode)
        Update the previous smoothed value for the pseudo-range.
        Parameters:
        smoothedCode - the previous smoothed value for the pseudo-range

      • updatePreviousSmoothingValue

        public void updatePreviousSmoothingValue​(double smoothingValue)
        Update the previous smoothing value.
        Parameters:
        smoothingValue - the previous smoothing value

      • addToCodeHistory

        public void addToCodeHistory​(double codeValue)
        Add a value to the history of the pseudo-range value.
        Parameters:
        codeValue - the value to add to the history

      • addToSmoothedCodeHistory

        public void addToSmoothedCodeHistory​(double smoothedCodeValue)
        Add a value to the history of the smoothed pseudo-range value.
        Parameters:
        smoothedCodeValue - the value to add to the history

      • resetFilterNext

        public void resetFilterNext​(double codeValue)
        Reset the filter in the case of a NaN phase value, skipping the smoothing at the present instant and initializing at the next one, keeping the current code value.
        Parameters:
        codeValue - pseudo range value before the reset.

      • resetNextBoolean

        protected void resetNextBoolean()
        Set the flag for resetting the filter to true.

      • resetK

        protected void resetK()
        Reset the current index of the filter to 1.

      • smoothedCode

        protected double smoothedCode​(double codeValue,
                              double smoothingValue)
        Computes the smoothed code value.

        This method corresponds to Eq. (4.23) of "Subirana, J. S., Hernandez-Pajares, M., and José Miguel Juan Zornoza. GNSS Data Processing: Fundamentals and Algorithms. European Space Agency."

        Parameters:
        codeValue - value of the input code measurement (non-smoothed)
        smoothingValue - value of the measurement used to smooth the code measurement
        Returns:
        the smoothed code value

      • checkValidData

        protected double checkValidData​(double codeValue,
                                double smoothedValue,
                                boolean cycleSlip)
        Checks if need to reset the filter or if cycle slip occurred.

        If yes, the smoothed value is reinitialized to the last code value. If no, the smoothed value value is not changed and the filter counter is updated.

        Parameters:
        codeValue - value of the input code measurement (non-smoothed)
        smoothedValue - the smoothed code value
        cycleSlip - true if cycle slip is detected
        Returns:
        the smoothed or non-smoothed value depending if the filter must be reseted