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In this study, we installed the Automatic Identification System (AIS) receiver on the Ieodo Ocean Research Station (IORS) from November 21 to 30, 2013 in order to monitor marine traffic and fishery activity in the jurisdictional sea area. The collected AIS raw data consist of static data report (MMSI, IMO NO., Call Sign, Ship Name, etc.) and position information report (position, speed, course, etc.), and the developed program was applied to classify ships according to ship flag and type information. The nationalities are released from the first three-digit numbers (MID) of MMSI, but in general most of small ships do not send an exact ship flag through Class B type AIS, a simplified and low-power equipment. From AIS data with flag information, ships under the flag of China had the highest frequency and the second was Korean flag, while in ship type cargo and fishing vessels were dominant in sequence. As for the ships without flag information, we compared the tracks with others in order to estimate ship flags. It can be said that fleets of ships with Chinese frequently appear sail together for fisheries over the waters, because the unknown ships followed a similar moving pattern with Chinese fishing vessels.

This paper presents results on the estimation of the phase velocity of internal waves (IWs) in the shallow waters of the South China Sea in terms of the water depth using satellite data. To calculate the phase velocity, two methods are considered. The first is based on the different positions of IW images acquired by Environmental Satelliteadvanced synthetic aperture radar (ASAR) and Terra-Moderate Resolution Imaging Spectroradiometer (MODIS) in a very short time interval, and the second method uses the images of several packets of IWs associated with semidiurnal tidal period in either a single ASAR or MODIS image. The former is termed as the multitemporal images (MTI) method, and the latter is referred to as the tidal period images (TPI) method. The results show that the wave velocities estimated by the MTI method have strong correlation with those derived from a depth-dependent IW propagation theory, while those by the TPI method have moderate correlation. Both the methods can be used to estimate the IW phase velocity but with reduced accuracy by the TPI method. The main reason of this reduced accuracy is the long tidal period during which the characteristics of IWs change as they propagate over long distance in the water of variable currents and/or bottom topography.