Extraction of coastal raft cultivation area with heterogeneous water background by thresholding object-based visually salient NDVI from high spatial resolution imagery

The development of high spatial resolution satellite imaging has enabled the acquisition of mariculture area information. This data could play an important role in mariculture investigations, ocean disaster evaluations, and coastal management. Because chlorophyll is concentrated in the widely distributed raft culture (a major kind of mariculture), the Normalized Difference Vegetation Index (NDVI) can be used for extraction. However, extensive coastal raft culture is easily confused with the heterogeneous water background. This results in unsatisfactory extraction when surveying a large water area with heterogeneous water background. By combining object-based image analysis and the centre-surround mechanism of a visual attention model, we propose an object-based visually salient NDVI (OBVS-NDVI) feature. Comparison experiments using Gaofen-2 spectral imagery of Luoyuan Bay, Fuzhou, China, indicate that OBVS-NDVI can effectively discriminate raft cultivation areas over large areas with a heterogeneous water background.