Research Lines: Mosaicing
seqence The mosaicing systems provide the means to construct visual maps of interest regions, thus providing an efficient means to monitor and observe the evolution of the oceanic dorsals.

The mosaicing system mainly consists in a mosaicing module and a down-looking camera. As the camera moves, the mosaicking system analyzes the images, computing the motion of the camera throughout the sequence while building a map of the visited area.

In order to track the motion, the system establishes feature correspondences between the consecutive images. This process is accomplished in two steps: (i ) the regions presenting high spatial gradient are selected by a corner detector and (ii ) the texture parameters of these regions are used as a matching vectors to be correlated with the next image. The use of texture parameters is critical to feature correlation since the underwater environment is usually poor on features. The set of textural proprieties were chosen to be as stable as possible when faced to lighting and camera position changes.

Once the correspondences are obtained, they can be used to compute the motion between the two images. The motion between two images can be modeled as a planar transformation described by a 3x3 matrix called homography, which relates the coordinate system of the images.

By using the obtained homographies, the images can be registered into a global frames and the merged together in order to generate a composite visual map of the visited region.