7. New technologies
7.1 DAC
7.1.1 An abbreviation of DAC is Dangerous Area of Collision which is an enclosed area of predict collision that to be based on setting the safe navigational distance around own ship.
When ship has be set own course avoiding this area, it can be expected her navigation with keeping a safe distance from other target ship. For example, in Fig... when own ship keeps the current course such as shown vector, own ship will enter DAC soon. In this case, the other target ship will enter into across the safe navigational distance area of own ship and it means dangerous to collision.
7.1.2 Creation of DAC
To form the display of DAC, it is necessary to set a safe navigational distance around own ship.
A set value of radius of CPA(closest point of approach) which has be used in ARPA for judgment of the margin of the distance to the dangerous of collision has to be applied as the size data of safe navigational distance area.
The DAC has to be calculated based on the set safe navigational distance area according to the other ship's speed and course and it has to be displayed as approximated to a polygon.
In the DAC display mode, PCP (Potential Collision Point) is also displayed in the end of the other target ship's course line, and the target and PCP are connected with a solid line.
When no PCP is exist, an intersection point of DAC and vector or its extension line of target are linked by dotted straight line Furthermore, when no intersection point of DAC is exist, only DAC and true vector of the target are displayed. Fig.7-1
Note:DAC has not to be displayed whose possibilities of collision to be low such as the following conditions, but true vector has to be displayed in this case.
─ The angle between a line connecting own ship and the target, and the relative vector of the target is greater than 90゜(which means that the other ship is going away gradually).
─ The distance to PCP is greater than 200nm.
─ The time to reach PCP exceeds 5 hours.
(OHP-12)
