The Acoustic ToolBox includes four acoustic models:

   BELLHOP: A beam/ray trace code

   KRAKEN:  A normal mode code

   SCOOTER: A finite element FFP code

   SPARC:   A time domain FFP code

A common input structure has been used throughout so that only minor
modifications are needed to switch from one program to another.

All the models produce shade files which can be processed
using a common set of plotting routines to plot transmission loss
vs. range or vs. range and depth.  These plotting routines
are contained in the GLOBAL directory.