The paper introduces algorithm for determining the relative positions of two shipsmanoeuvring as a pair. This algorithm also takes into account determination of angle γ,which is difference between present approaching vessel and guidance vessel course. Relativepositioning system is a vision system based on three colours LEDs matrix and rotatingCCD camera. There are presented ways of distance calculation based on photogrammetricmethods from the known distance between the characteristic points of the real. Severalpossible cases are taken into account. The considerations have been illustrated on thebasis of model of the system. These results confirm the correctness of the operation of the algorithm thatis used by the designed measuring system.
