model, fifty-five maneuvering rules were provided and each rule was
resolved by the first match theory. If no satisfactory maneuver was obtained although all
rules were checked, the size of the ellipse was reduced. This incidence was evaluated as a
navigator has too much load on his mind.
3.4 SUB-MODEL 4: PREVENTING FROM RUNNING AGROUND
Considering maneuvering characteristics of a vessel and how a navigator
set a limit to navigable water, it is appropriate to use an approximation with successive
linked segments instead of a complicated curved fathom line. If any one of these segments
lies in front of a vessel with in a safety distance in proportion to her velocity and
length, the course and speed on that occasion were not adopted as a way of maneuver to
prevent a collision because of the risk of running aground.
3.5 SUB-MODEL 5 : APPEARANCE AND DISAPPEARANCE OF VESSELS
Using the results of an observation on actual condition, zones where
vessels come in, its volume, distribution of length and speed and allocation of the routes
were arranged. The concrete location in each zone and time interval of each coming vessel
were given with normally and exponential distributed random numbers. The length and the
velocity of each vessel were given by using the random numbers adapted to the distribution
in actual condition. In this way, vessels appear and sail for their destination as they
maneuver to prevent a collision if necessary, and disappear when they leave the simulated
area or arrive at a port.
Fig.6 A sample of comparison under the same encounter situation.
The left is obtained from an experiment using the ship handling
simulator and the right is an output of this simulation model.
