Fig 1.
Diagram of a glider dive and acoustic coverage area with a downward-looking.
The relationship between the beam, dive angle and coverage dimensions is described in Eq 1.
Fig 2.
(a) The spatial form of the sampling beam is shown with `gridded bin ranges for the 10° glider beam. (b) The 3° beam definition applied in linear space, normalized and used as a multiplier for overlaid model space, to simulate the varying sensitivity in the sampling volume due to acoustic beam pattern.
Table 1.
Definition of the sampling platforms and associated echo-sounders.
Fig 3.
Normalized backscattering coefficient of (a) original generated target and appearance in data collected by (b) a typical glider, and (c) a typical ship.
Fig 4.
Simulation of insonified volume overlap showing (a) a typical glider with a dive angle of 26°, horizontal velocity of 0.25 ms-1 and beam range of 100 m, (b) a typical ship at the surface with a horizontal velocity of 5.14 ms-1 (10 knots) and beam range of 500 m. Total horizontal coverage in a 2 km mission by depth is shown for both platforms (c).
Fig 5.
The depth of a circular target is shown against apparent length of a circular target is shown against target diameter, and colored by apparent target length, simulated for (a) a ship and (b) a glider. (c) An example of target appearance is shown for a target of diameter 10 m (i) as it appears in the simulated (ii) ship data, and (iii) glider data.
Fig 6.
The maximum range at which two targets, each of 10 m diameter and with varying horizontal spacing could be distinguished as separate targets in simulated surveys shown.
Fig 7.
The measurement of a target total normalized backscattering coefficient as a percentage of the actual target is shown over a range of target horizontal velocities, sizes, depths and simulated survey platforms.