What is meaning of Distance Of Approach For Ships ?

Safety distance of approach (SDA)

The fundamental measure of ships passing is distance to closest point of approach (DCPA). Its value should be safety, it means:

DCPA ≥ DCPA min

Where:

DCPA =  distance to closest point of approach
DCPA min =  acceptable distance to closest point of approach.

Note:

The accident can happen; when above condition will not be performance. Knowing the number of entries of ships in a year (annual intensity of traffic), one can determine the probability of ships collision for one ship transit.