Under-Ice Sonar Visualization
The complexity of a data set such as ice keels lends itself perfectly to immersive visualization. The keel visualization environment displays sound energy in a volumetric form. Placing the user's viewpoint within that volume with a first-person perspective, rather than the current third-person perspective, should assist the observer.
Currently, the manipulation of the 3-D scene is dependent upon the standard keyboard and mouse. Planned upgrades to the under-ice visualization environment include a transition to an immersive display and 3-D gestural interface. The immersive display we have in mind is a head-mounted display. This design is portable and lends itself easily to use in tight quarters, such as those on a submarine.
When operating within a purely 3-D environment, the two-dimensional user interface becomes cumbersome. An elegant solution is to use a gestural interface in the form of a standard game pad with a sourceless inertial tracker attached. The object is to allow the user to position the viewpoint easily in any way. This functionality allows the user to better understand the complex visual representations of target strength and reverberation levels. Figure 9 demonstrates a prototype of the next step in the evolution of the UEV software.
A flexible, modularized, 3-D data fusion visualization system to study and data-mine under-ice acoustic information has widespread applicability for both military and civilian use. Building upon work originally sponsored by the Office of Naval Research (ONR) and years of Arctic experience, the Naval Undersea Warfare Center is developing pioneering visualizations for the integrated understanding of the acoustic properties of complex ocean environments, such as those under the pack ice in the Arctic Ocean and in shallow water coastal regions throughout the world.
Because the Linux operating system is so adaptable and generic, it has been easy to transform the software originally written for Silicon Graphics machines to run now on Linux. Furthermore, because the US Navy operates in both the Linux and Microsoft Windows environments, Linux has provided a cost-effective means to update, compile and test the UEV software. We have found that if the software compiles under Linux without errors, it almost always compiles under Visual C++, as long as the laborious process of ensuring all the Microsoft Windows paths are set up properly. Linux provides a unique environment for rapid prototyping, which results in software compatible with both UNIX and Microsoft Windows operating systems, thus qualifying as a valuable fleet software expeditor.
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Glossary of Terms
Acoustics: the physical properties of sound as they pertain to a particular situation.
Acoustic scattering time interval: the time interval in which a portion of the ice keel is being impacted by sound energy.
Data prospecting or data mining: the non-trivial extraction of implicit, previously unknown and potentially useful information from data.
Ensonification: impacting an object with sound energy.
Ice canopy: the ice cover formed by the ice pack.
Ice pack: a large expanse of floating ice.
Pack ice: ice making up the ice pack.
Sonar: the use of sound waves to detect underwater objects.
Stereopsis: 3-D vision, binocular vision and stereopsis mean the same thing.
Richard R. Shell is an electrical/computer engineer at the Naval Undersea Warfare Center Division, Newport, Rhode Island. He is a co-recipient of the NUWC 2003 Special Achievement Center Award for Technology Innovation for his work as part of the team that developed the TALOSS 3-D submarine undersea battlespace visualization software featured in the November 2003 issue of Linux Journal.
Garner C. Bishop received his BS in mathematics from Bates College in 1968 and his MS and PhD degrees in theoretical physics from the University of Connecticut in 1976 and 1982, respectively. In 1983, he began employment with the Naval Undersea Warfare Center, and from 1994 to 1996 he was a Visiting Lecturer in underwater acoustics at the University of Massachusetts, Dartmouth. He is a member of the Acoustic Society of America.
Douglas B. Maxwell is a mechanical engineer and research scientist at the NAVSEA Division Newport's Center for Advanced System Technology. His areas of expertise include design synthesis in virtual environments and synthetic training applications. He lives with his wife and dachshund in Newport, Rhode Island.
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