mil.navy.nps.rra
Class Ray

java.lang.Object
  |
  +--mil.navy.nps.rra.Ray

public class Ray

extends java.lang.Object

Ray implements the Recursive Ray Acoustics (rra) Algorithm derived by Professor Lawrence Ziomek to rapidly calculate a sound ray's 3D path through water, taking into account piecewise-local SSP, Surface and Bottom conditions.

Any wave front can be decomposed into a set of plane waves with the plane waves travelling in the direction of the normal to the wave front. The normal for each plane wave is defined by the normal to the wave front at the point where the front and the plane wave touch. The rra algorithm uses a difference-equation formulation of the ray theory solution to the linear acoustic wave equation. This provides a computationally rapid and theoretically general approach to simulate one ray on the surface of a wavefront as it propagates through the ocean. This makes rra an excellent choice to simulate underwater sonar under a very wide range of underwater environments.

Version:

1.0

Author:

LT Timothy M. Holliday USN

Contact: Don Brutzman (web.nps.navy.mil/~brutzman) brutzman@nps.navy.mil

Source Code:

~vrtp/mil/navy/nps/rra/Ray.java

http://devo.stl.nps.navy.mil/~brutzman/vrtp/mil/navy/nps/rra/Ray.java

History:

1 Nov 97	Timothy M. Holliday	New
17 Mar 98	Timothy M. Holliday	Added HTML comment convention
12 Apr 98	Timothy M. Holliday	Parameterless Constructors
14 Apr 98	Timothy M. Holliday	Simplified VRML Routines
10 Oct 98	Don Brutzman	Javadoc updates for jdk1.2b4
25 April 99	Don Brutzman	Javadoc updates for jdk1.2.1

Reference:

Holliday, Timothy, Real-Time 3D Sonar Modeling and Visualization, Master's Thesis, Naval Postgraduate School, Monterey California, June 1998. Available at vrtp/rra/HollidayRRAthesis.pdf. and devo.stl.nps.navy.mil/~brutzman/vrtp/rra/HollidayRRAthesis.pdf. Slideset available in Powerpoint and Acrobat .pdf formats.

See Also:

ExampleRay, Beam, Lobe

Constructor Summary

Ray()
Constructs a fixed size structure to trace a ray of acoustic energy through the ocean.

Method Summary

double	getAbsorption() This method returns the current total relaxation absorbtion in dB.
static boolean	getAppendLineFeed() This is a static method that returns the current line appendage.
double	getAzimuth() This method returns the azimuthal angle.
Bottom	getBottom() This method returns the handle to the bottom object.
int	getCount() This method returns the current number of points stored for the ray.
double	getDeltaTime() This method is returns the time step of the ray.
int	getDuration() This returns the ping duration.
double	getElevation() This method returns the elevation angle.
Vec3d	getNormal() This method returns the normal vector to the wavefront.
Vec3d	getPosition() This method gets the position of the ray.
double	getPositionX() This method returns the x-component of the position of the wavefront
double	getPositionY() This method returns the y-component of the position of the wavefront
double	getPositionZ() This method returns the z-component of the position of the wavefront
double	getReflectionPhase() This method returns the phase change of the wavefront
SSP	getSsp() This method returns the handle to the sound speed profile object.
Surface	getSurface() This method returns the handle to the surface object.
double	getTime() This method returns the current simulation time.
double	getTime(int index) This method returns a saved simulation time.
Vec3d	getTrailingPosition() This method returns the position of the trailing edge of the wavefront
java.lang.String	normalizedTime(int N, double endtime) This method returns the requested normalized time as a string.
java.lang.String	position(int N) This method returns the requested position as a String.
void	Propagate(double timeStep) This method causes the ray to propagate one timestep into the future.
void	recordPoint() This method forces a recording of the current ray position.
boolean	reflected() This method returns whether or not the ray has been reflected in the most recent time step.
void	reset() This method resets all of the ray parameters after instantiation has occurred since reuse is more time efficient than garbage collection and reallocation.
static void	setAppendLineFeed(boolean pAppendLineFeed) This is a static method used to indicate whether a line feed is desired at the end of every line.
void	setAzimuth(double phi) This method sets the azimuthal angle, which is the angle from the x-axis to the z-axis rotating about the y-axis.
void	setBottom(Bottom pBottom) This method sets the handle to the bottom object.
void	setDeltaTime(double deltaTime) This method is used to change the time step of the ray after instanciation.
void	setDuration(int duration) This method sets the ping duration.
void	setElevation(double beta) This method sets the elevation angle, which is the angle from the y-axis to the x-axis rotating about the z-axis.
void	setPosition(double x, double y, double z) This method sets the position of the ray.
void	setSsp(SSP pSsp) This method sets the handle to the sound speed profile object.
void	setSurface(Surface pSurface) This method sets the handle to the surface object.
double	totalCurvature() This returns the total curvature of the ray path since the last recorded point.
java.lang.String	trailingPosition(int N) This method returns the requested trailing edge of the ray as a String.

Methods inherited from class java.lang.Object

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

Constructor Detail

Ray

public Ray()

Constructs a fixed size structure to trace a ray of acoustic energy through the ocean. Use accessor methods to set initial values of member variables.

Method Detail

reset

public void reset()

This method resets all of the ray parameters after instantiation has occurred since reuse is more time efficient than garbage collection and reallocation.

getNormal

public Vec3d getNormal()

This method returns the normal vector to the wavefront.

setAzimuth

public void setAzimuth(double phi)

This method sets the azimuthal angle, which is the angle from the x-axis to the z-axis rotating about the y-axis.

getAzimuth

public double getAzimuth()

This method returns the azimuthal angle.

setElevation

public void setElevation(double beta)

This method sets the elevation angle, which is the angle from the y-axis to the x-axis rotating about the z-axis.

getElevation

public double getElevation()

This method returns the elevation angle.

setPosition

public void setPosition(double x,
                        double y,
                        double z)

This method sets the position of the ray.

getPosition

public Vec3d getPosition()

This method gets the position of the ray.

setDeltaTime

public void setDeltaTime(double deltaTime)

This method is used to change the time step of the ray after instanciation.

getDeltaTime

public double getDeltaTime()

This method is returns the time step of the ray.

setDuration

public void setDuration(int duration)

This method sets the ping duration. Duration is currently 1 or 2. The integer refers to the number of deltaTime increments.

getDuration

public int getDuration()

This returns the ping duration. Duration is currently 1 or 2. The integer refers to the number of deltaTime increments.

setBottom

public void setBottom(Bottom pBottom)

This method sets the handle to the bottom object.

getBottom

public Bottom getBottom()

This method returns the handle to the bottom object.

setSurface

public void setSurface(Surface pSurface)

This method sets the handle to the surface object.

getSurface

public Surface getSurface()

This method returns the handle to the surface object.

setSsp

public void setSsp(SSP pSsp)

This method sets the handle to the sound speed profile object.

getSsp

public SSP getSsp()

This method returns the handle to the sound speed profile object.

getReflectionPhase

public double getReflectionPhase()

This method returns the phase change of the wavefront

getPositionX

public double getPositionX()

This method returns the x-component of the position of the wavefront

getPositionY

public double getPositionY()

This method returns the y-component of the position of the wavefront

getPositionZ

public double getPositionZ()

This method returns the z-component of the position of the wavefront

getTrailingPosition

public Vec3d getTrailingPosition()

This method returns the position of the trailing edge of the wavefront

getTime

public double getTime()

This method returns the current simulation time.

getTime

public double getTime(int index)

This method returns a saved simulation time.

Propagate

public void Propagate(double timeStep)

This method causes the ray to propagate one timestep into the future.

getCount

public int getCount()

This method returns the current number of points stored for the ray.

getAbsorption

public double getAbsorption()

This method returns the current total relaxation absorbtion in dB.

reflected

public boolean reflected()

This method returns whether or not the ray has been reflected in the most recent time step.

recordPoint

public void recordPoint()

This method forces a recording of the current ray position. It also forces the total curvature of the ray since the last recorded point to 0.0.

totalCurvature

public double totalCurvature()

This returns the total curvature of the ray path since the last recorded point. The curvature of a small segment of curve can be approximated by the curvature of a circle which is the change in angular position around the circle divided by the pathlength change. K = deltaTheta/deltaPathLength. Thus total curvature is the sum of the curvatures of the small segments along a ray trajectory.

position

public java.lang.String position(int N)

This method returns the requested position as a String.

trailingPosition

public java.lang.String trailingPosition(int N)

This method returns the requested trailing edge of the ray as a String.

normalizedTime

public java.lang.String normalizedTime(int N,
                                       double endtime)

This method returns the requested normalized time as a string.

setAppendLineFeed

public static void setAppendLineFeed(boolean pAppendLineFeed)

This is a static method used to indicate whether a line feed is desired at the end of every line. 'true' indicates a linefeed is desired and 'false' indicates that a space is desired"

getAppendLineFeed

public static boolean getAppendLineFeed()

This is a static method that returns the current line appendage.