Servicio de Información Comunitario sobre Investigación y Desarrollo - CORDIS

Validation and verification

Validation and verification activities in OCEANIDES give an understanding of the relative performance of various oil spill detection approaches in satellite images and of the number of false positives and negatives one could expect, under favourable meteorological conditions, in radar satellite images. Algorithms and procedures for detecting slicks from Synthetic Aperture Radar (SAR) satellite imagery have been benchmarked against each other and against observations from aircraft in order to arrive at a common definition and estimation of false positives and negatives. A clear procedure has been set-up to calculate in a uniform way the probability that a shape seen on an image is indeed an oil slick and, conversely, to define what meteo conditions and SAR mode combination make it likely that a real oil slick would be undiscovered.

Two different campaigns aiming at verifying oil slicks observations in satellite images by aircraft were executed. During both campaigns, aircrafts were sent to examine slicks observed in RADARSAT and ENVISAT images downloaded at Tromsø Satellite Receiving Station and analysed in Near Real Time mode. In most cases it was possible to transmit the slick position to the aircraft within an hour from the acquisition.

The number of false positive increases, as one might expect, as the operator s confidence diminishes. On the other hand it should be noted that in case of high confidence level (i.e. when all the relevant peculiar characteristics of an oil slick as detected in a radar image are present) the false positive rate is virtually zero.
Despite the low number of cases to be analysed and the fact that additional activities might need to be continued in the future in a systematic way to reach firmer conclusions, OCEANIDES has to be considered as an important step forward in the efforts to provide a clearer view on the reliability of satellite observation of oil slicks. The process OCEANIDES has launched needs to be continued and further extended in a systematic way since it is instrumental to establish an operational routine use of satellite observations.

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Federal Institute of Hydrology
P.O.Box 20 02 53
56002 Kobkenz
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