Oil Spill Remote Sensing

Remote sensing for oil spills is assessed. The technical aspects of sensors are reviewed and the benefits and limitations of each sensor are given. The use of visible techniques is ubiquitous; however, it gives only the same results as visible monitoring. Oil has no particular spectral features that would allow for identification among the many possible background interferences. Identification of specific oil types is not possible. Cameras are only useful to provide documentation. Infrared (IR) offers some potential as an oil spill sensor. In daytime, oil absorbs light and remits this as thermal energy at temperatures 3–8 K above ambient. IR cameras are economical; however, they suffer from problems such as the inability to discriminate oil on beaches; among weeds, debris, or sediment; and under certain lighting conditions. Furthermore, water-in-oil emulsions are often not detected in the IR. The laser fluorosensor is a useful instrument because of its unique capability to identify oil on backgrounds that include water, soil, weeds, ice, and snow. It is the only sensor that can positively discriminate oil on most backgrounds. The laser fluorosensor also allows for positive identification and discrimination between oil types. Radar detects oil on water only in that oil will dampen water-surface capillary waves under low to moderate wave/wind conditions. Radar offers the only potential for large-area searches and day/night and foul weather remote sensing. Radar is costly, requires a dedicated aircraft, and is prone to many interferences. False targets can be as high as 95%. Satellite-borne radar sensors are useful; however, their frequency of overpass and lesser spatial resolution render them useful for mapping large spills or assisting in ship and platform discharge monitoring. Equipment that measures relative slick thickness is not available at this time and is still under development. Passive microwave has been studied for several years, but many commercial instruments lack sufficient spatial resolution to be practical, operational instruments. A laser-acoustic instrument, which provides the only technology to measure absolute oil thickness, has been successfully tested but is not in production.