Methodology for the estimation of ocean surface currents using region matching and differential algorithms

The ocean involves a complex set of physical, chemical, biological and geological processes, interacting each other to influence our climate and natural environment. One of the most important disciplines in oceanography is the study of the ocean dynamics. Particularly, ocean surface circulation can be recovered by the automated tracking of thermal features (coastal upwellings, filaments and eddies) in pairs of sequential satellite imagery. This paper presents a new methodology for the automatic estimation of ocean surface currents using AVHRR and MODIS imagery. The technique is based on a two-step process: precise structure detection followed by the structure tracking. The precise detection methodology is, as well, composed by two modules. The first one with the goal to obtain a coarse structure segmentation and the second achieving the maximum detail of the structure. The tracking methodology estimates motion fields using region matching and differential techniques with additional modules to guarantee the optimum performance. Twelve matching metrics and four differential algorithms were implemented and tested. Information from the previous structure segmentation stage is of fundamental importance to initialize the optimum motion estimation parameters and to generate the corresponding study area for each sequence. The proposed methodology, combining the segmentation and tracking steps, has been extensively tested and it has demonstrated an adequate performance in the estimation of flow fields in multitemporal and multisensorial sequences of the NW African coast.