Review of Autonomous Undersea Vehicle (AUV) Developments 
The ocean's response to the atmosphere, radiant energy, and tides may be characterized according to its 
local depth. The domains are the deep ocean (depths greater than 1,000 m), the continental slopes 
(depths from 2,000 m to 200 m), the continental shelf (depths from 200 m to 20 m), and the near-shore 
littoral zone (depths shallower than 50 m). A thorough understanding and modeling of near-shore littoral 
waters is critically important for future naval forces. A physical understanding is reasonably well 
established, but this zone also encompasses much greater variability in current, sediment transport, 
visibility, salinity, and so on, than the deeper regions of the ocean. The physical variability, the acoustic 
environment, and the visibility of the littoral zones are not well modeled. Each region on Earth is affected 
differently primarily because of variations in bottom topography, water runoff, climate, and bottom 
composition. There are, however, well-understood (except for turbulence) physical principles to assist in 
characterizing each regime. If appropriate data are acquired and retrospective studies performed, it is 
possible to anticipate the physical state of the littoral zone that might be encountered in naval operations. 
Multimodality sensor systems that provide real-time data are being developed for this highly variable 
environment. 
Model scenarios for each potential area could be developed and validated. Codes, climatologies, 
topographic configurations, and the like, can be stored in a modern high-speed, large-memory 
workstation. Modern data assimilation protocols (either variational adjoint or Kalman-Bucy filtering) can 
be overlaid on the basic model database. Either in anticipation of actions or during an event, all data 
gathered in the region can be assimilated to produce the most probable physical environment needed for 
surface, underwater, acoustic, and countermeasure operations. 
The data output from these physical models is time dependent and three-dimensional. Shipboard 
personnel generally do not have the technical background to interpret the complex environmental fields. 
A solution is to develop four-dimensional graphical visualization systems to be used to identify patterns of 
such phenomena as currents, temperature fronts, and low-visibility regions. Such software is not 
currently available except in primitive form but is under development. 
Mapping the shape of the bottom is currently straightforward, but visualization of the flow in the water 
volume is difficult because of the enormous databases involved and the inherent problem of mapping a 
four-dimensional picture onto a two-dimensional computer screen. Workstations of the future will have 
enough cycle power, memory, and storage to handle the computations, but new visualization techniques 
have to be developed, such as four-dimensional virtual reality systems. Within 10 years, it should be 
possible to provide on shipboard modest-sized virtual-reality sites for naval personnel to see the present 
and evolving underwater physical environment. 
The physics of acoustic phenomena in the open ocean is well understood. Given a source location, a 
receiver, and information on such things as water density and the shape of the bottom, the behavior of 
sound can be calculated. But in most littoral zones, this is almost impossible because the temperature 
and salinity of the water change with season and weather conditions. Moreover, surface sea waves 
change quickly and frequently and the behavior of the bottom reflectivity and absorption changes within 
waters. Thus, reliable interpretation of acoustic transmission in near-shore waters is technologically 
challenging. 
Unfortunately, foreign navies are investing in electric submarines that are relatively small and quiet. 
These, along with inexpensive and plentiful mines, pose serious threats to naval forces in shallow water. 
Special attention needs to be directed toward pattern recognition and signal recognition of moving and 
stationary objects in shallow water. Extensive simulation of acoustic systems must be carried out with the 
various scenarios predicted by the physical modeling system. For example, high-frequency active sonar 
may be effective for mine detection in shallow water but not have enough range for ASW in deeper water. 
Modeling will provide the information necessary to make informed choices of sensor-system deployment 
and enable the development of protocols to identify interdicted structures not encountered in tests of the 
anticipated acoustic environments." 
This panel made the following recommendations: 
“Battle-space awareness, communications, target identification, navigation, weapon guidance, and 
tactical planning all require real-time understanding and forecasting of the atmospheric, space, and sea 
environments of operation. Global weather models with improved satellite data on winds, temperature, 
solar inputs, and so on will permit the generation of accurate weather forecasts. Space weather 
