Package Localiser.algorithms.genericLocaliser

Class Chi2TimeDelays

java.lang.Object
Localiser.algorithms.genericLocaliser.Chi2TimeDelays
All Implemented Interfaces:
MinimisationFunction
public class Chi2TimeDelays extends Object implements MinimisationFunction
Minimisation function for a localisation performed using time delay calculations. This can be used with any PAMGuard minimisation algorithm;

The time delay minimisation function is based on a set of observed time delays. A generic structure for observed time delays is used.

Each row in the time delay ArrayList contains a group time delays calculated from N synchrnoised hydrophones in the corresponding ArrayListinvalid input: '<'ArrayList> row. This allows potential locaisation between large groups of unsynchronised hydrophones, a situation always encountered during target motions analysis.

Author:
Jamie Macaulay

  • Field Details

    • speedOfSound

      protected double speedOfSound
      The speed of sound in meters per second.

  • Constructor Details

    • Chi2TimeDelays

      public Chi2TimeDelays()
      Chi2 time delays

    • Chi2TimeDelays

      public Chi2TimeDelays(ArrayList<ArrayList<Double>> timeDelaysObs, ArrayList<ArrayList<Double>> timeDelayErrors, ArrayList<ArrayList<double[]>> hydrophoneArray)
      Chi2 time delays.
      Parameters:
      timeDelaysObs - - the observed time delays in seconds
      timeDelayErrors - - the time delay errors in seconds
      hydrophoneArray - - the hydrophone arrays.

  • Method Details

    • value

      public double value(double[] sourceLoc)
      Description copied from interface: MinimisationFunction
      Return the Chi2 value at a specified 'location'/ for a set of points which can be used to generated expected data that is then used to calculated a chi2 value with observed data. Example location might be [x y z] location to generate time delays which are then compared to expected time delays.
      Specified by:
      value in interface MinimisationFunction
      Parameters:
      sourceLoc - - the point at which chi2 value is to be calculated;
      Returns:
      the chi2 value.

    • getDim

      public int getDim()
      Description copied from interface: MinimisationFunction
      Get the simulation dimensions e.g. if solving for [x y z] location getDim()=3;
      Specified by:
      getDim in interface MinimisationFunction

    • chiSquared

      public static double chiSquared(ArrayList<ArrayList<Double>> observedTimeDelays, ArrayList<ArrayList<Double>> chainPosTimeDelays, ArrayList<ArrayList<Double>> errors)
      Calculates the chi^2 value between observed data and theoretical delays calculated for a certain point in space.
      Parameters:
      observedTimeDelays - - the observed time delays (seconds).
      chainPosTimeDelays - - the set of time delays to compare to the observed time delays (seconds).
      errors - - the measurement errors in the observed time delays.
      Returns:
      chi squared value for observed time delays compared to chain position time delays.

    • calcTimeDelays

      public static ArrayList<ArrayList<Double>> calcTimeDelays(double[] sourceLoc, ArrayList<ArrayList<double[]>> hydrophonePos, double speedOfSound)
      Calculate the theoretical time delays if a source was located at position in space. (Technically space can be any number of dimensions but probably useful to stick to 3D)
      Parameters:
      sourceLoc - - theoretical position of the source.
      hydrophonePos - - the positions of all the hydrophones within the array in Cartesian coOrdinates.
      speedOfSound - - the speed of sound in meters per second.
      Returns:
      The time delays that would result from a source at this location.

    • setTimeDelays

      public void setTimeDelays(ArrayList<ArrayList<Double>> timeDelays)
      Set the time delays. Each row is a set for delays from N synchronised hydrophones. Different rows can have different numbers of synchronised hydrophones.
      Parameters:
      timeDelays - - a set of time delays in seconds.

    • setTimeDelaysErrors

      public void setTimeDelaysErrors(ArrayList<ArrayList<Double>> timeDelayErrors)
      Parameters:
      timeDelayErrors -

    • setHydrophonePos

      public void setHydrophonePos(ArrayList<ArrayList<double[]>> hydrophonePos)
      Set the hydrophone positions
      Parameters:
      hydrophonePos - - the hydrophone positions.

    • addTimingError

      public static ArrayList<ArrayList<Double>> addTimingError(ArrayList<ArrayList<Double>> timeDelayErrors, double timeError, float sampleRate)
      Adds the a constant timing error to the time delays error array e.g. this could be used to add an average cross correlation timing error.
      Parameters:
      timeDelayErrors - - list of time delay errors.
      timeError - - the timing error to add, in samples
      sampleRate - - the sample rate in samples per second.
      Returns:
      an array with the timeError added appropriately to each measurement.

    • getFirstStep

      public double[] getFirstStep()
      Description copied from interface: MinimisationFunction
      Get first search jump (often not needed)
      Specified by:
      getFirstStep in interface MinimisationFunction
      Returns:
      first jump location with getDim() dimensions.

    • getSpeedOfSound

      public double getSpeedOfSound()
      // * Get the sound speed.
      Returns:
      - the sound speed in meters per second

    • setSpeedOfSound

      public void setSpeedOfSound(double speedOfSound)
      Set the sound speed.
      Parameters:
      speedOfSound - - the sound speed in meters per second.

    • getStart

      public double[] getStart()
      Description copied from interface: MinimisationFunction
      Get starting position for search algorithm.
      Specified by:
      getStart in interface MinimisationFunction
      Returns:
      starting location with getDim() dimensions.

    • setStart

      public void setStart(double[] start)
      Set the start location for the algorithm. If null then a random first step is assigned.
      Parameters:
      start - location. Must be the same length as number of dimensions

    • setFirstStep

      public void setFirstStep(double[] firstStep)
      Set the start location for the algorithm. If null then a random location is selected
      Parameters:
      start - location. Must be the same length as number of dimensions