Altimetric anomalies of geostrophic velocities are added to each MDT, in order to produce the full ocean currents, then compared to concurrent drifter velocities. Differences (in rms) are due to smoothing differences between altimetry and lagrangian data, noise in each data set, and MDT errors. Because we use exactly the same set of data, the lowest differences correspond to the more precise MDT. Vectorial correlation are also computed (Cv).

Differences are particularly high in the Gulf Stream area were currents are intense, and differences between drifter velocity and satellite altimetric deduced velocities are larger.