. "Appendix D: Hydrodynamics, Physical Models, and Mathematical Modeling." Simulated Voyages: Using Simulation Technology to Train and License Mariners. Washington, DC: The National Academies Press, 1996.
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made it practical to combine actual radar equipment with mathematical models of vessel behavior to create radar simulators for use as an element of full-mission or multi-task training or as a limited-task or special-task stand-alone training device.
Full-mission, multi-task, and limited-task simulators are, as a rule, operated in real time2 and can appear to be highly realistic. The amount of realism is referred to as "face" or "apparent" validity (NRC, 1992).3 Ship-bridge simulators are used for all types of operational scenarios. Important issues in the use of computer-based marine simulation include:
whether all of the appropriate vessel maneuverability cues are present in the simulation or correctly portrayed,
whether the maneuvering response of the ship is actually correct, and
the relative importance of accuracy in these areas (NRC, 1992).
Development of ship-bridge simulators and simulations is more complex than development of commercial air carrier simulators. Development of visual flight simulators for the commercial air carrier industry is linked directly to the development of specific airframes. The simulators are not modified to permit training on multiple airframes (NRC, 1992). This practice is possible because of the large numbers of similar airframes owned and operated by commercial airlines.
Ship-bridge simulators are developed independent of the vessels they simulate and are routinely adjusted to permit training in other hull forms and sizes. As a result, some simulator facilities use either a number of models to meet the specific application needs of training sponsors or adjust their model to simulate a different type or size vessel. If these adjustments are not correct, the resulting trajectory predictions are inaccurate, regardless of the quality of the algorithms used or the apparent validity of the simulation. For these reasons, it is appropriate to validate each trajectory prediction model or perturbation in a model to determine the capabilities and limitations of the product being delivered to the trainer, the marine licensing authority, and licensing examiners and assessors.
Radar simulators are an example of effective use of limited-task simulation for mariner training. Radar simulators, first used for mariner training in the 1960s, were developed separately from ship-bridge simulators. They used
Combined real-time and fast-time computer-based simulations have been used outside the commercial maritime sector, for example, to minimize the delay between planned learning scenarios.
Sometimes training simulations are run in fast time to bring trainees quickly to learning situations, which are then run in real time, such as surface warfare simulations. This approach has not been common with the use of ship-bridge simulators for training merchant mariners.