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14
Getting Started
Map/Sonar Split &
Sonar Pages
Map/Sonar Split Page
The Map/Sonar Split Page combines the Map Page on the left half with the Sonar Page on the right by
default. You may adjust the size of the split (pg 32). Press PAGE key to proceed to the Sonar Page.
Sonar Page
The Sonar Page is where your GPSMAP 178/178C Sounder becomes a powerful fishfinder. The top
left of the screen contains data fields, while the Adjustment Bar above the data fields allows direct access
to the settings most commonly changed while using the Sonar Page. 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 which reflects the depth of the area being displayed. If the
unit does not detect a transducer attached to the unit, a “Sonar Turned Off” message appears across the
Sonar Page. You may also show a sonar flasher and color bar on the right side.
The sonar display may 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 (see pg. 34). For
example, you may choose to show dual frequency at a 2X zoom (Dual 2X) on one half and normal range
dual frequency (Dual) returns on the other half. The current display mode is displayed at the bottom of
each sonar display.
(172C) Sonar returns show as red (strongest), then oranges (strong), yellows (medium), greens
(weaker) and blues (weakest). (172) The stronger sonar returns are darker, weaker returns are displayed
in a lighter shade of gray. The ‘Fish Symbols’ option (see page 38) allows you to view the actual sonar
data, a fish symbol, or a combination of both. ‘Fish Symbols’ appear as green (172C), or dark gray (172).
When the unit is set to ‘Dual’ frequency (see page 35), the appearance of the fish symbols (and simulated
fish returns) changes. Fish symbols from the narrower beam (200kHz) are solid (or narrow returns), but
the symbols from the wider beam (50kHz) are hollow (or wide returns). Fish icons are displayed in three
different sizes. Actual fish returns may not always appear as perfect arches, due to the speed, fish orienta-
tion, and/or other conditions.
More on understanding the Sonar Page may be found on page 33 and in Appendix G.
Dual frequency returns
Sonar Page
Data Fields
Depth
Scale
Adjustment
Menu
Simulated
Fish Arch
Bottom
Thermocline
Center beam
return
Outer edge
beam returns
Frequency
mode
Flasher