| 摘要 |
<p>A marine sodar system (10) is provided for use on board ship to determine the presence or absence of an evaporative duct in the vicinity of the ship. In one form the system comprises port and starboard transmitters (12p and 12s) and respectively associated port and starboard receivers (14p and 14s) mounted on the mast (16) of a ship (18). Transmitters (12p and 12s) generate pulsed acoustic beams (2Op and 20s) which are narrow in elevation and wide in azimuth while receivers (14p and 14s) have antenna lobes (22p and 22s) that are wide in elevation and narrow in azimuth. Thus, starboard transmitter (12s) illuminates an elongate strip (24s) of the sea surface extending in parallel spaced relation to ship (18) while receiver (14s) interrogates an elongate strip (26s) of the sea surface extending outward orthogonal to the ship. Strips (24s) and (26s) overlap only in a relatively small area (28s) so that echoes of the transmitted signal arising from this area are selectively detected by receiver (14s). The same situation exists on the port side of the ship (18). Returned echoes are processed by the receivers to determine the presence or absence of the duct. Other embodiments are described and the invention is concerned with marine sodar apparatus, marine sodar systems and with shipboard sodar methods of detecting evaporative ducts while at sea.</p> |
