Package Localiser.algorithms

Class Correlations

java.lang.Object
Localiser.algorithms.Correlations
public class Correlations extends Object
Author:
Doug Gillespie

Various functions to do with cross correlating two or more signals

As with the FastFFT class, these functions are no longer static so that Allocation of FFT internal storage is done separately for each detector. This avoids it having to be continually reallocated if fft's of different lenghts are taken.

Also calculates a delay correction factor based on a parabolic interpolation around the maximum value. For compatibility with previous versions, the returned results is still the integer solution. If you require greater accuracy, you should get the interpolated correction and add this to the main integer result for double precision accuracy.

  • Constructor Details

    • Correlations

      public Correlations()

  • Method Details

    • getDelay

      public TimeDelayData getDelay(double[] s1, double[] s2, DelayMeasurementParams delayMeasurementParams, double sampleRate, int fftLength)
      Measure the time delay between pulses on two channels.
      Parameters:
      delayMeasurementParams - Measurement parameters.
      fftLength - FFT length to use (data will be packed or truncated as necessary)
      f1 - waveform on channel 1
      f2 - waveform on channel 2
      Returns:
      time delay in samples.

    • getDelay

      public TimeDelayData getDelay(double[] s1, double[] s2, DelayMeasurementParams delayMeasurementParams, double sampleRate, int fftLength, double maxDelaySamples)
      Measure the time delay between pulses on two channels.
      Parameters:
      delayMeasurementParams - Measurement parameters.
      fftLength - FFT length to use (data will be packed or truncated as necessary)
      maxDelaySamples - Maximum possible delay in samples
      f1 - waveform on channel 1
      f2 - waveform on channel 2
      Returns:
      time delay in samples.

    • getDelay

      public TimeDelayData getDelay(ComplexArray f1, ComplexArray f2, DelayMeasurementParams delayMeasurementParams, double sampleRate, int fftLength)
      Measure the time delay between pulses on two channels. Inputs in this case are the spectrum data (most of the cross correlation is done in the frequency domain)
      Parameters:
      f1 - complex spectrum on channel 1
      f2 - complex spectrum on channel 2
      delayMeasurementParams - Measurement parameters.
      fftLength - FFT length to use (data will be packed or truncated as necessary)
      Returns:
      time delay in samples.

    • getDelay

      public TimeDelayData getDelay(ComplexArray complexArray, ComplexArray complexArray2, DelayMeasurementParams delayMeasurementParams, double sampleRate, int fftLength, double maxDelaySamples)
      Measure the time delay between pulses on two channels. Inputs in this case are the spectrum data (most of the cross correlation is done in the frequency domain)
      Parameters:
      complexArray - complex spectrum on channel 1
      complexArray2 - complex spectrum on channel 2
      delayMeasurementParams - Measurement parameters.
      fftLength - FFT length to use (data will be packed or truncated as necessary)
      maxDelaySamples - Maximum feasible delay between channels.
      Returns:
      time delay in samples.

    • getDelay

      public TimeDelayData getDelay(ComplexArray f1, ComplexArray f2, int fftLength, double maxDelay, int[] binRange)
      Measure the time delay between pulses on two channels. Inputs in this case are the spectrum data (most of the cross correlation is done in the frequency domain)

      This was the public function called from the click detector, but now that we've added DelayMEasurementParams to the main call, this is to be called privately only once the filtering and envelope manipulations specified in the params have all been dealt with.

      Parameters:
      f1 - complex spectrum on channel 1
      f2 - complex spectrum on channel 2
      fftLength - FFT length to use (data will be packed or truncated as necessary)
      maxDelay - Maximum feasible delay between channels.
      binRnage - - the bin range to use.
      Returns:
      time delay in samples.

    • getCorrelationValue

      public double getCorrelationValue()
      Get the value of the last correlation calculated by any of the functions in the class.
      Returns:
      the correlationValue

    • defaultTimingError

      public static double defaultTimingError(float sampleRate)
      Generate a default timing error which is 1/sqrt(12) times the sample interval
      Parameters:
      sampleRate - sample rate
      Returns:
      typical timing error

    • parabolicCorrection

      public double parabolicCorrection(double y1, double y2, double y3)
      Calculate a parabolic fit correction based on three bin heights
      The answer should always be between -0.5 and +0.5
      Parameters:
      y1 - first bin
      y2 - second bin
      y3 - third bin
      Returns:
      correction = 0.5*(y3-y1)/(2*y2-y1-y3);

    • parabolicHeight

      public double parabolicHeight(double y1, double y2, double y3)
      Calculate a parabolic maximum height based on three bin heights
      Parameters:
      y1 - first bin
      y2 - second bin
      y3 - third bin
      Returns:
      height of parabola through those points.

    • parabolicHeight

      public double parabolicHeight(double time, double[] correlationFunction)
      Parameters:
      correlationFunction - correlation function.
      t - time to measure height at.
      Returns:
      height of parabola through those points.

    • getCorrelation

      public double[] getCorrelation(double[] wave1, double[] wave2, boolean normalise)
      Get the correlation function of waves 1 and 2 and normalise if requested.
      Parameters:
      wave1 - - the first wave.
      wave2 - - the second wave.
      normalise - - true to normalise.
      Returns:
      the correlation function.

    • getInterpolatedPeak

      public double[] getInterpolatedPeak(ComplexArray complexData, double scale, double maxDelay)
      Get the peak position and the peak height from a complex array returned by the ifft function.
      Parameters:
      complexData - Complex data from the ifft during cross correlation calculation
      scale - Scaling factor (sqrt(sum^2 of each channel))
      maxDelay - max searchable delay
      Returns:
      two element array giving the peak pos and it's height.

    • getInterpolatedPeak

      public double[] getInterpolatedPeak(double[] invFFTData, double scale, double maxDelay)

    • getInterpolatedPeak

      public double[] getInterpolatedPeak(Complex[] complexData, double scale, double maxDelay)
      Get the peak position and the peak height from a complex array returned by the ifft function.
      Parameters:
      complexData - Complex data from the ifft during cross correlation calculation
      scale - Scaling factor (sqrt(sum^2 of each channel))
      maxDelay - max searchable delay
      Returns:
      two element array giving the peak pos and it's height.

    • getInterpolatedPeak

      public double[] getInterpolatedPeak(double[] corrFunction)
      Find the peak of a correlation function, interpolating about each peak using a wee parabola.

      Note that first and last bins are not used in the search.

      Parameters:
      corrFunction - correlation function
      Returns:
      peak position and peak height.

    • getInterpolatedMaxima

      public double[][] getInterpolatedMaxima(double[] corrFunction)
      Get interpolated maxima around every peak in the correlation function.
      Parameters:
      corrFunction - correlation function.
      Returns:
      2d array of times and interpolated values.

    • getMaxDelays

      public double[] getMaxDelays(float sampleRate, int groupHydrophones, long currentMillis)
      Get the maximum permissible delays in samples for the set of hydrophones. These numbers can be used to limit the range of correlation searches to valid values.
      Parameters:
      sampleRate - sample rate of the data
      groupHydrophones - bitmap of used hydrophones.
      Returns:
      array of maximum time delays in samples.

    • getFastFFT

      public FastFFT getFastFFT()
      Returns:
      the fastFFT

    • getLastCorrelationData

      public double[] getLastCorrelationData()
      Returns:
      the lastCorrelationData

    • setLastCorrelationData

      public void setLastCorrelationData(double[] lastCorrelationData)
      Parameters:
      lastCorrelationData - the lastCorrelationData to set

    • getLastPeak

      public double[] getLastPeak()
      Returns:
      the lastPeak

    • setLastPeak

      public void setLastPeak(double[] lastPeak)
      Parameters:
      lastPeak - the lastPeak to set