Garmin GPSMap 498 Owner's Manual - Page 81

Understanding the Sonar Display, solid colors blue is the default. - cover

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Narrow Beam Wide Beam The wide beam is more helpful in shallow water, because it gives you a much wider view of objects in the water, including areas beyond the sides of your boat. At a 30-foot depth, the wide beam covers the area of approximately a 20-foot circle. GPSMAP 392/398/492/498 Owner's Manual USING SONAR > SONAR PAGE Understanding the Sonar Display One of the first things to understand about sonar is that the transducer sends a beam down to the bottom of the water, much like the beam of a flashlight. The beam starts small near your vessel and expands as it gets to the bottom. The Sonar Page does not show a 3-D representation of the underwater environment. Instead, the display is in two dimensions, much like if you took a picture of an aquarium. Only the depth of the item in the water is shown. The strongest sonar returns appear on your screen as the most intense solid color (depending on your selected color scheme; red is the default). The weakest returns appear as the less intense, less solid colors (blue is the default). The bottom of the water is always be the strongest signal, and therefore the most intense color. The bottom is the continuous, intensely-colored line running across the bottom of the screen. The GPSMAP 392/398/492/498 uses the latest technology in interpreting bottom signals; it can see through fish, structures, and thermoclines (shown in the weakest colors). However, large schools of fish or dense structures close to the bottom can affect water depth return readings. NOTE: If the GPSMAP 392/398/492/498 is unable to track the bottom for any reason, the digits in the depth window flash on and off to alert you that the unit is not tracking the bottom. 73

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GPSMAP 392/398/492/498 Owner’s Manual
73
U
SING
S
ONAR
>
S
ONAR
P
AGE
Wide Beam
Narrow Beam
The wide beam is more helpful in shallow water, because it gives
you a much wider view of objects in the water, including areas
beyond the sides of your boat. At a 30-foot depth, the wide beam
covers the area of approximately a 20-foot circle.
Understanding the Sonar Display
One of the first things to understand about sonar is that the
transducer sends a beam down to the bottom of the water, much
like the beam of a flashlight. The beam starts small near your vessel
and expands as it gets to the bottom.
The Sonar Page does not show a 3-D representation of the
underwater environment. Instead, the display is in two dimensions,
much like if you took a picture of an aquarium. Only the depth of
the item in the water is shown.
The strongest sonar returns appear on your screen as the most
intense solid color (depending on your selected color scheme; red
is the default). The weakest returns appear as the less intense, less
solid colors (blue is the default).
The bottom of the water is always be the strongest signal, and
therefore the most intense color. The bottom is the continuous,
intensely-colored line running across the bottom of the screen.
The GPSMAP 392/398/492/498 uses the latest technology in
interpreting bottom signals; it can see through fish, structures,
and thermoclines (shown in the weakest colors). However, large
schools of fish or dense structures close to the bottom can affect
water depth return readings.
NOTE:
If the GPSMAP 392/398/492/498 is unable to track the
bottom for any reason, the digits in the depth window flash on
and off to alert you that the unit is not tracking the bottom.