A fishfinder
is a type of fathometer, both being specialized types of echo sounding
systems, a type of Active
SONAR.
('Sounding' is the measurement of water depth, a historical nautical term
of very long usage.) The fishfinder uses active sonar to detect fish and 'the
bottom' and displays them on a graphical display device, generally a LCD or
CRT screen. In contrast, the modern fathometer (from fathom plus meter, as
in 'to measure') is designed specifically to show depth, so may use only a
digital display (useless for fish finding) instead of a graphical display,
and frequently will have some means of making a permanent recording of soundings
(which are merely shown and subsequently electronically discarded in common
sporting fishfinder technology) and are always principally instruments of
navigation and safety.
The distinction is in their main purpose and hence in the features given the
system. Both work the same way, and use similar frequencies, and, display
type permitting, both can show fish and the bottom. Thus today, both have
merged, especially with the advent of computer interfaced multipurpose fishfinders
combining
GPS technology, digital chart-plotting, perhaps
RADAR and electronic
compass displays in the same affordable sporting unit.
