Current ellipse
From Glossary of Meteorology
current ellipse
A graphic representation (a hodograph) of a rotary current (of a tidal current, or a harmonic component of a tidal current, during a complete tidal cycle) in which the velocity of the current at different hours of the tidal cycle is represented by radius vectors and vector angles.
A line joining the extremities of the radius vectors will form a curve roughly approximating an ellipse.