||Every port has its unique design and hydrographic conditions that when a vessel is preparing to inbound or outbound of a harbor the local pilot will help the captain to maneuver the vessel against the winds and currents to pass safely the breakwater. This research applies the AIS (Automatic Identification System) of vessels and sea states to search for their relationships. The AIS data includes ship speed, course, heading, size, latitude, longitude, time etc. Sea states include winds, currents, tides, and waves. As a navigation controller at Kaohsiung Second Port, my experiences suggest that vessels within 8 nautical miles off breakwater is a reasonable distance for my study. The data are selected from a huge data base of the 15 to 16 of every month in 2015.|
The first step is to check the data quality. Basic statistic boxplot is applied to AIS data. Cruise tracks are plotted for inbound and outbound vessels. The anchored vessels are eliminated. The basic data quality control shows large amount of AIS are no good for further analysis. Time series of sea states data and basic statistics were carried out. Selected data from these two data sets are combined for correlation coefficient and Principle Component Analysis.
We divided ship length of every 50 m as a category, and correlated with sea states. The results show that winds and currents are closely correlated with headings and ship speeds. The differences of headings to courses are negatively correlated to currents of the north-south direction. Also, the differences get larger when in slow ship speed. However, the differences of heading to courses of ship size of over 350m are mainly related to winds. For the correlation of winds and currents itself, tidal current dominated when wind is small and wind has little influence to the currents.