Introduction & Background

jAtrak is a tool for visualising the data output from a seismic raytracing package called ATRAK. You don't require ATRAK to use jAtrak because jAtrak is supplied with a number of example data files produced by ATRAK.

What is a Seismic Raytracing Package?
Geophysicists analyse what is under the surface of the earth using sound. As a sound wave travels through the different layers of rock it is refracted and reflected in a similar way to light passing through a glass block. If you know where the light entered the block and left the block you can begin to understand something about the block itself. Seismology works on a similar principle, by setting off controlled sound waves on the surface of the earth and recording where they emerge we can start to understand what is under the surface without starting to dig!

The ATRAK Seismic Raytracing Package simply uses a computer to simulate this process.

	ATRAK
The Model above represents the boundaries between the different layers of rock. The green layer is the surface of the earth.		ATRAK takes the model on the left and simulates the paths that sound waves will take through the rock. As you can see the lines change direction slighty at each boundary.

What does jAtrak do?
jAtrak produces a 3D image of the Model and Rays. This model is produced using 3D graphics so that a user may manipulate the image using the mouse. jAtrak also allows the image to be saved to file or printed.

What ATRAK files does jAtrak Require?
jAtrak reads data from two files, a Model file and a Ray file. The Model file is a binary file containing the data describing the boundaries between the rocks and the Ray file is a binary file containing the paths of the Rays. jAtrak contains examples of both of these files so you don't require ATRAK to use jAtrak!

Prerequisites

• JRE (ver 1.3 or higher) - www.javasoft.com
• Java3D (VERSION 1.2.*, NOT 1.3) - www.javasoft.com
• A standard 3D graphics card.

Setting up your environment to run jAtrak shouldn't be complicated. The code has been successfully run on Windows, Linux and Solaris platforms. As it is written in Java you should be able to run it on any platform that supports Java and Java3D.
You will need to:

1. Install the JRE.
2. Install Java3D. Note that Java3D requires that you have an implementation of OpenGL/DirectX on your machine. The documentation for Java3D clearly explains what you will need.
3. Test Java3D to make sure it is working properly. There are a number of sample programs with the Java3D installation which you can use to test it.
4. Run jAtrak using the most recent release.

Controls

Version 1 of the system was designed to be as simple as possible to use. The window containing the Model and Rays is manipulated by using the mouse and some simple key presses.

When rotating the geometry using the mouse don't be surprised if the Model and Rays disappear, this is by design! The Model and Rays will reappear after a couple of seconds.

Be patient the first time you press the 'P' key, the snap-shot window sometimes takes a while to appear. Subsequent windows will be created very quickly.

Get the Software

Download the most recent release from http://sourceforge.net/projects/jatrak/

Remember that you will need Java 1.3 or above and Java3D in order to use the software.

Contact

For specific enquiries about the jATRAK code contact: ciknowles@hotmail.com. Chris programs for a living and wrote the bulk of the jAtrak library in his spare time.

For enquiries regarding integration of jAtrak and ATRAK contact jwookey@users.sourceforge.net. James works at the University of Leeds in the Geophysics department. There isn't much he doesn't know about Atrak.

If you are interested in extending or using any part of jAtrak we would very keen to talk to you.