The minimum distance (usually in nautical miles) between the vessels at the moment of closest approach.
The CPA is traditionally calculated using vector geometry. Determine Relative Velocity ( Vrcap V sub r Ocean CPA method.pdf
Recent research, such as that found on ScienceDirect and ResearchGate , suggests improving basic CPA by: The minimum distance (usually in nautical miles) between
The is the estimated position where the distance between two ships (the "own ship" and a "target vessel") reaches its absolute minimum. It is the primary metric used by Watchkeeping Officers to assess the Risk of Collision (ROC) . If the CPA is too small, a collision is possible, requiring immediate maneuvering according to COLREGs . 2. Core Parameters The method relies on two primary mathematical outputs: a collision is possible