Using the sonar page – Garmin GPSMAP 190-00683-00 User Manual

Page 112

Using the Sonar Page

When combined with a GSD 21 Sounder Module, your GPSMAP

378/478 becomes a powerful fishfinder/flasher with the Sonar Page.

If a GSD 21 is attached, but the unit does not detect a transducer,

a “Sonar Turned Off” message appears across the Sonar Page. The

Sonar Page appears only if a GSD 21 has ever been attached or

when the unit is in Simulator Mode.
The middle of the page contains a right-to-left moving sonar image

of the water beneath your boat. Items appear as they pass under your

transducer. Those items on the right side of the screen are closer to

you than those on the left. Along the right side of the screen is an

adjustable scale that reflects the depth of the area being shown. The

top left corner shows the adjustment option, the depth, and the water

temperature.

Sonar Page

The sonar returns show as red (strongest), then orange (strong),

yellow (medium), green (weaker), and blue (weakest). The Fish

Symbols option allows you to view the actual sonar data, a fish

symbol or a combination of both. When the unit is set to Dual, the

appearance of the fish symbols changes. Fish symbols from the

center of the beam (200 kHz) are solid (or narrow arches), but the

returns from the edges of the beam (50 kHz) are hollow (or wide

arches).
The sonar display can also be set to show a split screen view of a

zoomed portion of the sonar, bottom lock (display scaled from the

bottom up), or a combination of these options. For example, you

can choose to show dual frequency at a 2X zoom (Dual 2X) on one

half and normal range dual frequency (Dual) on the other half. The

current display mode appears at the bottom of each sonar display.
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