An Overview of Next-Generation Underwater Target Detection and Tracking: An Integrated Underwater Architecture <s> E. HORIZONTAL -GRADIENT ACOUSTICAL RAY -TRACE PROGRAM TRIMAIN <s> Ray paths are found in a medium with a sound speed varying in two dimensions. The velocity field is approximated in a triangular region by a linear function of range and depth. The assumed velocity is continuous, but the gradient of the velocity is discontinuous across the boundaries of the triangular region. Results are compared with exact solutions for a tilted bilinear profile, and tilted and nontilted hyperbolic cosine profiles. The errors in ray position are due to the linear approximation of the velocity, not to the existence of horizontal gradients. <s> BIB001 </s> An Overview of Next-Generation Underwater Target Detection and Tracking: An Integrated Underwater Architecture <s> E. HORIZONTAL -GRADIENT ACOUSTICAL RAY -TRACE PROGRAM TRIMAIN <s> Abstract : Interest has arisen in the last few years to develop analytical models of the undersea acoustic environment which are suitable for use on digital computers. To realistically represent the sound-field structure which exists in the ocean, one must consider the variation of sound speed in two dimensions: depth and range. A computer program, TRIMAIN, was written in Fortran 4 in which the sound-speed field for a given region is divided into triangular segments of the range-and-depth plane. Four types of intensity calculations are available: a completely random phase summation, a completely coherent phase summation, a statistical influence over depth, and an average over a convergence zone. Additional output options are ray depth distributions, ray printplots, and Calcomp ray plots, including plots of input sound speeds and of bathymetric profiles. <s> BIB002
A FORTRAN-IV program (initially written as FORTRAN-63 BIB001 ) is used to compute intensity level, travel time, and source and receiver angles for individual eigenrays. Ray paths are calculated in a 2D medium with varying SSP. The velocity is assumed to be constant in piecewise linear functions of depth and range. The constant velocity is continuous in a triangular region however; its gradient is discontinuous at the triangular boundaries. TRIMAIN has the following features: • No limitations for SSPs are introduced in this program. Also, SSPs are presented as a function of range and depth. • Different rays can be traced at the same time. • The program presents variable-bottom in piecewise linear function of depth. • The sea surface is flat with a user-specified constant reflection coefficient and phase shift. The program uses depth, frequency, surface loss, bottom loss, and volume attenuation as input files and transmission losses, surface and bottom reflections, eigenray as output files. There are some cautions to run this program, otherwise the program ends at any point during simulations. The number of input points in SSP is limited to 50. Source depth and sound speed depth should be different. 1000 rays should be traced by the program. The program uses original ray theory. Modifications are open for any interested user. Caustics are solved in this program by throwing the eigenray out for those two rays whose depth is 0.001 meter close to each other BIB002 .