Fig. 5.

(a) Horizontal distances of the ship (dots) and the fish (the other symbols) from the receiver (OBEM2) along the survey line (positive distance is toward the east from the receiver along the survey line), (b) horizontal distance between the ship and the fish, and (c) ship speed, are all plotted against time. Each symbol in (a) and (b) indicates its data source; distance measurement from the fish to OBEM1 (circles), OBEM2 (crosses), or OBEM3 (triangles), as shown in Fig. 4. It is worth noting that the horizontal distance between the ship and the fish is in proportion to the tilt angle of the towed bipole source when the tilt angle is small, and that a tilt angle of 1 degree corresponds to 63 m in the horizontal distance between the ship and the fish in this case.