of manned models, a development borne out of practical necessity to safely train the prospective masters of very large crude carriers in shiphandling. The scaling inherent in manned models is believed by many to enhance training effectiveness, although there are questions regarding the effect of scaling factors on individuals who do not have a well-established frame of reference in the operation of ships of the categories being simulated.

Because computer-based simulations rely primarily on software-based mathematical algorithms, there is considerable flexibility that could be used to deliberately depart from realism. In marine simulation, however, the opposite approach has been the rule. To build and improve confidence among mariners, training sponsors, and marine licensing authorities, there are strong pressures to use the highest level of realism possible. Nevertheless, it is possible to alter the mathematical trajectory prediction models to accentuate certain vessel maneuvering behavior, for example, as an instructional technique to assist a trainee in becoming aware of this behavior. As a rule, such an approach is problematic, because it appears that only a few ship-bridge simulation staffs have the level of sophistication in instructional design and hydrodynamic modeling to effectively stage and control deliberate departures from realism.

A major technical consideration in the application of simulators and simulations is the need for consistently reproducible results from simulation exercises. Currently, there are no standards for the development, operation, or modification of simulators or simulations. As their use is expanded from training to performance evaluation, licensing assessment, and substitution of training for sea time, consideration needs to be given to the establishment of industrywide criteria and standards.

PHYSICAL AND MATHEMATICAL SIMULATION MODELS

From the modeler's perspective, the simulation user must specify the accuracy needed for particular training or licensing objectives. The simulation modeler (for physical models or computer-based models) can then assess whether that accuracy can be provided. Pilots, for instance, need very accurate models to properly portray bank effects and other complex interactions, whereas a less robust model may suffice to introduce very basic operational concepts and procedures to beginners. A detailed discussion of the hydrodynamic, physical models, mathematical models, and research needs in these areas is included in Appendix D.

Ship-Bridge Simulator Models

Current ship-bridge simulations are based on mathematical models derived by extrapolating hydrodynamic coefficients from towing-tank tests for a restricted



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