An Overview of Next-Generation Underwater Target Detection and Tracking: An Integrated Underwater Architecture <s> C. WAVE-FRONT QUEUE 3D (WaveQ3D) <s> Summary. An asymptotic procedure for the computation of wave fields in two-dimensional laterally inhomogeneous media is proposed. It is based on the simulation of the wave field by a system of Gaussian beams. Each beam is continued independently through an arbitrary inhomogeneous structure. The complete wave field at a receiver is then obtained as an integral superposition of all Gaussian beams arriving in some neighbourhood of the receiver. The corresponding integral formula is valid even in various singular regions where the ray method fails (the vicinity of caustic, critical point, etc.). Numerical examples are given. <s> BIB001 </s> An Overview of Next-Generation Underwater Target Detection and Tracking: An Integrated Underwater Architecture <s> C. WAVE-FRONT QUEUE 3D (WaveQ3D) <s> Abstract The current generations of the HUGIN autonomous underwater vehicles (AUVs) have been used in a number of Rapid Environmental Assessment (REA) missions over the past few years, including participation in several national and international military exercises and operations. This article discusses some of the main advantages and limitations of using AUVs in REA operations. This is followed by examples from actual operations that illustrate the choices and trade-offs that must be made. The article aims to demonstrate that AUVs are mature enough for many types of REA operations. <s> BIB002
WaveQ3D is a 3D ray tracing model especially designed for active sonar simulation systems and distributed as part of Under Sea Modeling Library (USML). It is based on ray theory where other models (e.g., parabolic equation and normal mode) exhibit low performance for frequencies above 1000 Hz. The objective of this model is to generate transmission loss eigenrays accurately only for coastal scenarios. Moreover, it generates other eigenrays products also i.e., multipath travel time, phase, and propagation direction. WaveQ3D enhances Gaussian beam techniques to make it applicable for lower frequencies also. These Gaussian beam techniques are based on Gaussian Ray Bundling (GRAB) BIB001 , BIB002 . Due to its unique characteristic of enhances Gaussian beam techniques; it can solve Eikon equation in spherical Earth coordinates, thereby supporting out-ofplane 3D effects. Real time active sonar simulation systems exhibit better performance when the number of targets to be detected is smaller than the number of ray tracing points. However, WaveQ3D does not support this assumption for planned missions. With an increase in number of targets, WaveQ3D performs faster with less overhead based on each target. The accuracy of this model for sea surface is not yet guaranteed  .