The accuracy of ARPA (Automated radar plotting aid) calculations is a problem on which manufacturers and researchers have worked ever since the system was created. The elements of the situation of passing a target followed, as calculated by ARPA, are an important parameter for the safety of shipping. Nowadays the usage of ARPA as a part of the integrated bridge navigation system (IBNS) and its inclusion in the process of ship steering has raised new questions to the accuracy of the calculations. Analyses show that the factors taken into account, distance to the target and drift, play a crucial role. Their manifestation in the mode of steering the ship on a pre-set route, however, is in a manner which is different from those known so far. The present article analyses the influence of the drift and the distance to the target on the accuracy of ARPA calculations as an element of IBNS and the differences resulting from the manner of the stabilization of the ship’s movement. Measurements with aids to navigation during passage in the region of the East China Sea are used.