If you're looking for a complete navigation unit, the Garmin GPSMAP 178C Sounder
may be just what you want. Its a GPS chartplotter with integrated sonar that
lets you plot your way and locate fish, old wrecks, or any other underwater
Whether you're on a lake or an ocean, being able to see below the water surface
is at least a help and sometimes a necessity. The Garmin 178C Sounder
goes beyond regular GPS receivers to do just that. The unit comes with either
a single frequency or duel frequency transducer. With the duel frequencies, you
get better resolution for the same coverage area. Either way, you get a real-time
image of the water and anything in it as it passes under your boat.
Sound waves from the transducer bounce off any objects below the surface and
the returning sound waves are displayed as different colors according to their
intensity. Water can have layers with different rates of temperature change and
are called "thermoclines". Fish are often attracted to thermoclines and the
Garmin GPSMAP 178C lets you identify both the thermoclines and the fish. The unit can
even detect whether the bottom is hard or soft.
The depth range on the 178C can be set to track the bottom or stay at one
specified distance. You also can adjust the reception sensitivity to filter
out unwanted detail or use the zoom feature to check out areas of interest.
When you do find something of interest, the 178C Sounder can store it as an
underwater waypoint. These waypoints are tagged with the date, time and water
temperature. This makes them particularly useful for returning to spots where
fish gather. And with the receiver's split screen you can view the navigation chart
while also watching what's happening below.
All this information would be useless without a good display and the Garmin
178C delivers. The 3.2" square display (4.5" diagonal) is a reliable 256-color
LCD. A 200 MHz processor creates fast chart redraws and sonar scans. The
high-contrast image stands out even in bright sunlight. At night or low light
levels, the adjustable fluorescent backlighting keeps the display just as easy
to read. The waterproof case fully protects the display and receiver, no matter
where its mounted.
While the sonar helps you locate fish, the basemap of the 178C GPS receiver
helps you get to where they are. The built-in worldwide map covers the roads
to get you to the water and the shorelines of rivers, lakes, and oceans. You
can name and make comments for up to 3000 waypoints. And if you ever are just
out exploring and want to return to your starting point, the TracBack feature can
help. The track log automatically records turns as waypoints, so your path will
have been identified and you merely retrace your steps.
If you need maps with greater detail, the Garmin GPSMAP 178C uses memory cards
to hold the map data. You transfer map data from your computer to the memory card using
the supplied interface cable. The map data can come from Garmin's MapSource
or BlueChart data series, for either inland or offshore boating.
The Garmin GPSMAP 178C Sounder is powered off the boat's battery having a range
of 10 to 35 volts. The single knob tilt and swivel mount can be located anywhere the
unit will get clear satellite reception. Or the receiver can also be mounted below
deck or flush in a panel, if an external antenna is used. To achieve the most
accurate location data, the 178C is Wide Area Augmentation System (WAAS) and
Differential GPS (DGPS) ready. And for emergency situations, the 178C receiver can
even send, receive and display position data using a Digital Selective Calling (DSC)
equipped VHF radio.