A Practical Approach for Analysing SPI Images

Sediment profile imagery (SPI) is a remote sensing technique that is used for determining whether the marine sediments provide the suitable habitat for benthic (bottom-dwelling) fauna. The SPI technique is based on an inverse periscope that penetrates the seabed and the captured images are analysed in order to evaluate the activity of the resident marine fauna and the overall level of sediment contamination. Although this sediment monitoring technique has been widely used by the marine benthic scientists for several years, SPI analysis is based on a visual qualitative and quantitative evaluation performed by the human operator. Independent tests reveal that this method is affected in terms of sensitivity and reproductibility by the subjectivism of the human operator. This paper describes the development of a color-based image processing technique that is applied to decide if the imaged sediment contains an oxidised layer and to detect its area and position within the image. A number of experimental results are presented and discussed.