Surface Velocities From Multiple-Tracer Image Sequences

We discuss a new inverse model to estimate surface velocity using an image sequence with more than one tracer. The method employs the global optimal solution technique, which covers an image scene with subarrays or tiles, within which both velocity components are specified as bilinear forms. Substitution into the tracer conservation equation for each tracer yields a system of equations for the velocity field, which is constrained to fit the image data in a least-squares sense over the entire image domain. Solution is achieved iteratively by a Gauss-Seidel method. A numerical model is used as a benchmark to examine the accuracy of this new technique. Image pairs from the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments onboard the NASA Terra and Aqua spacecraft and the hyperspectral imager for the coastal ocean instrument currently onboard the International Space Station are also used to demonstrate the new inverse model with actual ocean data. The derived vector field from MODIS is then compared with the velocity field obtained by the single-tracer technique, and the results are found to be qualitatively equivalent.