In the USA, a method of determing optimum routes was developed at the end of the 50s which made use in particular of the relationship between the vessel speed and the seaway (height and direction of forward movement of waves). ###>A la fin des années 50, on a mis au point aux Etats­ltais une méthode de détermination des routes optimales, qui fait appel notamment aux rapports entre vitesse du bateau et haute mer (creux et direction des vagues).