Eagle 640c 操作指南

50

Fish Symbols vs. Full Sonar Chart
You may have noticed in the quick reference we used fish arches in full
sonar chart mode for our example instead of the popular Fish I.D.

 fish

symbol feature. Here's why.

Fish I.D. is an easier way for a sonar novice to recognize a fishy signal
return when he sees it. However, locating fish by symbol only has some
limitations.

Your sonar unit's microprocessor is remarkably powerful but it can be
fooled. Some of the echoes calculated to be fish could be tree limbs or
turtles.  To see what's under your boat in maximum detail, we recom-
mend you turn off Fish I.D. and begin learning to interpret fish arches.

Fish I.D. is most handy when you're in another part of the boat or per-
forming some task that prevents you from watching the sonar screen.
Then, you can turn on Fish I.D. and the audible fish alarm. When that
lunker swims under your boat, you'll hear it!

Fish I.D. can also be useful when you want to screen out some of the
sonar detail gathered by your unit. For example, in one case a fisher-
man in San Francisco Bay saw clouds of clutter in the water but no fish
arches. When a down rigger was pulled up it brought up several small
jellyfish. The fisherman switched the sonar to Fish I.D., which screened
out the schools of jellyfish and clearly showed the game fish as fish
symbols.

Other Free Training Aids
The sonar options section discusses Fish I.D., fish alarms and other fea-
tures in greater detail. If you or a friend has Internet access, you can
also learn more about interpreting what you see on your sonar screen.
Visit our web site, 

. Be sure to check out the

free Sonar Tutorial, which includes animated illustrations and more
pictures of actual sonar returns, all described in detail. A "printer
friendly" version of the tutorial is available on our web site. It makes a
great supplement to this manual.