# Oil Spill Monitoring of Shipborne Radar Image Features Using SVM and Local Adaptive Threshold
## 1 Introduction  
Oil, including crude, gasoline, bulk oil, and fuel, spills into marine environments during off-shore well production, oil refining, oil tanker transportation, and pipeline ruptures. According to the European Space Agency (ESA), the amount of oil spilled annually worldwide is estimated to be more than 4.5 million tons, and 80% of this is due to operative discharges [1]. This has become a major man-made threat to marine and coastal environments, with adverse long-term impacts on economics and biological health [2]. For example, a recent oil spill disaster has continued to pollute many of Brazil's coastlines for months, with the catastrophe exhausting the resources of the government and communities [3; 4]. Marine oil spills can diffuse extensively the sea surface within several hours, leading to very serious consequences [5]. Billions of dollars are spent preventing pollution, but risk cannot be completely eliminated [6]. Technologies that can detect and monitor oil spills are, therefore, very important for rapid emergency response and contamination control. With the ability to rapidly determine the scope and location of oil spills, remote sensing plays an increasingly important role in the emergency response of marine oil spills [7]. Among the remotesensing sensors, ultraviolet instruments, infrared detectors, microwave radiometers, and radar have been used to in an attempt to monitor oil spills [8]. Ultraviolet sensors can measure oil film thickness below 10 microns, but the correlation between thin oil slick and oil spill cleaning is very low, so the use of ultraviolet sensors for oil spills is minimal [9; 10; 11]. Infrared detectors are less expensive than other remote sensing sensors, but because the thermal radiation of seaweed is similar to that of an oil spill, the result can be falsely, requiring verification by other means [12; 13]. Infrared sensors can work perfectly in the absence of clouds, rain, and fog [14]. Microwave radiometer sensors are relatively costly and complex for monitoring an oil spill and measuring oil thickness. A microwave radiometer can only work accurately with adequate environmental and oil property data. Furthermore, the results may be biased, with few interferences, and in practice, microwave radiometer sensors have not been used for monitoring oil spills [9; 14]. Radar has been widely used in the research and application of monitoring oil spills, because it provides a long detection distance and is not limited by time and weather conditions [15; 16; 17]. Radar is the most widely used sensor on spaceborne, airborne, and shipborne platforms. More spaceborne synthetic aperture radar (SAR) oil spill monitoring research has been published because its fine spatial-resolution data are publicly accessible [18]. SAR oil spill detection can be summarized as (a) dark area detection, (b) feature extraction, and (c) discrimination between oil slicks and lookalikes [19; 20]. The results are mostly used for liability and damage assessment because of the revisit time, which is not adequately frequent for ensuring good oil spill sampling [21]. Although this time interval is a key drawback, the application of spaceborne radar has played a major role in promoting the development of remote sensing for monitoring oil spills [22]. The application of airborne radar can compensate for the time interval shortcoming in the data acquisition of spaceborne radar, and research concerning remote sensing for the marine oil spill monitoring of airborne radar is increasing [23]. Initially, helicopter-borne radar was used to obtain the distribution range of oil films above the sea surface, but the emergence of the unmanned aerial vehicle (UAV) has greatly reduced the cost of airborne radar application [24]. The key disadvantage of airborne radar is that it cannot operate in severe weather [9]. Shipborne radar can overcome certain severe weather and can monitor oil spill in real-time with the cruise of the decontamination ship, and this has the potential for broad applicability.