7.1.3 Display example of DAC Fig.7-2
(OHP-13)
When own ship speed is same or faster than the other target ship.
1] This is an example of indication that it is possible to pass through both of bow side and aft side of the target ship with keeping set CPA limit value.
However, if own ship goes straight as it is, she will enter DAC area.
To avoid DAC, if own ship goes on the course at near side to the target (at the right side of the figure), own ship will pass through aft side of the target ship and if own ship goes on the course at far side from the target (at left side of the figure), own ship will pass through bow side of the target ship.
2] In this case, it is impossible for own ship to pass through bow side of the ship with keeping set CPA limit value because own ship and the other target ship are at the same speed.
3] Although this is almost the same as 2], but no PCP exist.
When own ship speed is slower than the other target ship.
4] This is an example of indication with two DACs. The characteristic of DAC near the target is the same as that in 1], however the characteristic of DAC far from the target is reverse.
Which is inversely if own ship goes on the course at far side from the target, own ship will pass through after the target ship.
This difference is resulted from the fact that going forward DAC at the near side to the target means own ship going toward the target ship, and going forward DAC at the far side from the target means own ship going away from the target ship.
In this way, sometimes becomes impossible to keep the safe navigational distance with the target ship(the worst case is collision) because two DACs come near gradually and will be combined as one DAC in the end. (in case of 5] and 7]).
When this kind of two DACs are displayed, the navigator do not choice course between the DACs.
To take such a course unavoidable, be fully careful and watch of changing the other ship's apeed and own ship speed.
5] This is an example of indication that two DACs in 4] are combined.
Own ship cannot pass through bow side of the target ship with keeping set CPA limit value, that is, if own ship goes on the course at near side to the target(the left side of the figure) or goes on the course at the far side form the target(the right side of the figure), own ship will go through aft side of the target ship.
This kind of DAC is displayed with a dotted line and can be distinguished from general DAC (DAC which can pass through bow side of the target ship).
