org.orekit.estimation.measurements.filtering

Class SingleFrequencyHatchFilter

java.lang.Object

org.orekit.estimation.measurements.filtering.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 Summary

Constructors

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

Method Summary

Modifier and Type	Method and Description
void	addToCodeHistory(double codeValue) Add a value to the history of the pseudo-range value.
void	addToSmoothedCodeHistory(double smoothedCodeValue) Add a value to the history of the smoothed pseudo-range value.
protected double	checkValidData(double codeValue, double smoothedValue, boolean cycleSlip) Checks if need to reset the filter or if cycle slip occurred.
ObservationData	filterData(ObservationData codeData, ObservationData smoothingData) This method filters the provided data given the state of the filter.
ArrayList<Double>	getCodeHistory() Get the history of the pseudo-range values used by the filter.
ArrayList<Double>	getSmoothedCodeHistory() Get the history of the smoothed pseudo-range values used by the filter.
double	getThreshold() Get the threshold for loss of lock detection.
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.
protected void	resetK() Reset the current index of the filter to 1.
protected void	resetNextBoolean() Set the flag for resetting the filter to true.
protected double	smoothedCode(double codeValue, double smoothingValue) Computes the smoothed code value.
void	updatePreviousSmoothedCode(double smoothedCode) Update the previous smoothed value for the pseudo-range.
void	updatePreviousSmoothingValue(double smoothingValue) Update the previous smoothing value.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

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