Firstly, we should estimate the locations and speeds of all the vessels at the examining time Tj. Since those vessels may take 30–60 min to pass through a certain leg, we thus determine that the systems will be examined twice per hour (48 times per day). We shall apply the recent improvements to process the AIS data for location and speed estimation purposes ( Van Dorp et al., 2001 and Van Dorp and Merrick, 2009). Let