I. Introduction
Ships play an irreplaceable role in transportation by carrying over 80% of the world’s trade [1]. It is thus important to monitor ship positions and navigation status for safety and economic reasons. For a considerable period of time in the past, ship monitoring was mainly done by full-time maritime staff, who may be fatigued after working for a long time, resulting in the inability to achieve sustainable monitoring. Over the past decade, the burst of artificial intelligence techniques has led to the rapid development of unmanned means of ship monitoring, where ship perception usually takes an important role [2], [3], [4], [5].