Glossary.

Antipodal Point.   A location on the surface of the earth which is diametrically opposite another point. If you are standing at any point on the surface of the earth, and you were to drill a hole directly downward through the exact centre of the earth,  your drill would pop out at your antipodal point. Straight-line paths over the surface of the earth between antipodal points (often called 'Great Circle Routes') are infinitely numerous and all of the same length.

​CUGFS. Columbia University Geophysical Field Station.  There were several 'field stations' run by Columbia University.

CUGFS-B.   Designation given to the Bermuda site (The SOFAR Station) of the Columbia University Geophysical Field Station 'network.

Drum Recorder.  A device that continuously displays the signal received from a hydrophone as a paper record.  See here for further information.

PDR.    Precision Depth Recorder.  An instrument that, when connected to a ship's transducer, could accurately determine the depth of water under the ship.  The prototype was developed at SOFAR in the late '40s. 

PGI.   Palisades Geophysical Institute.  The change of name that 'Sofar' made when Columbia University was forced to abandon all it's Field Stations that were doing military research.

Ping.        As applied to underwater acoustics, a very short sound signal sent into the ocean from a transducer (usually mounted on the bottom of the hull of a ship), which is used to determine the presence of objects in the ocean (and the ocean bottom), and their distances from the ship.

SHL.   The research vessel 'Sir Horace Lamb', based in St. George's, Bermuda, owned and operated by SOFAR.  She was a 136' converted minesweeper, formerly the USS Redpoll.

SOFAR.     SOund Fixing And  Ranging.  As applied to Underwater acoustics, the process of
determining the distance and direction of a sound source from a listening  position.

SOFAR Bomb.  An explosive device which is designed to sink into the ocean to a specified depth before detonating.  There were several depths available, (shallow, medium or deep), and several sizes of explosive available from 1/4 lb to 2 lb of TNT.

SOFAR Station.   An Oceanographic research station specializing in underwater acoustics, located at the Eastern end of St. David's Island in Bermuda.

Sound Channel Axis.  A fancy name for a layer of water found in all the oceans where a sound signal becomes trapped, and will travel for vast distances.  The depth of this layer varies from very close to the surface in polar water to 2,500 feet in warm water.

Transducer.    A device located underwater on the ship’s hull that can send out a brief signal (a 'ping’), and receive back an echo from any object from which the ping is reflected.   Knowing the speed of sound in seawater, (about 4,800 ft/sec.) the distance to the object can be calculated.