FLIR RAYMARINE A98 - 15.11 The sonar image

15.10 Dual channel ping modes
The CP570 sonar module features 2 CHIRP sonar
channels that can transmit and receive independently
of each other. Ping modes are available that balance
the ping rate Vs interference between the 2 channels.
Ping modes:
• Auto — The system selects the best mode based
on your chosen range settings.
• Independent pings — Maximum ping rate, but
greater chance of interference.
• Simultaneous pings — Reduced ping rate,
based on the deepest range setting, but reduced
chance of interference.
Note: Ping modes will only be available when
the sonar module is connected to a 2 channel
transducer.
Selecting a ping mode
From the Sonar application menu:
1. Select Set-up.
2. Select Sounder Set-up.
3. Select Dual-Channel Ping Modes.
The ping mode selection page is displayed.
4. Select the required ping mode.
15.11 The sonar image
Interpreting the bottom using sonar
It is important to understand how to correctly interpret
the bottom structure represented on-screen.
The bottom usually produces a strong echo.
The following images show how different bottom
conditions are represented on-screen:
Item Description
1
A hard bottom (sand) produces a thin line.
2
A soft bottom (mud or seaweed cover) produces
a wide line.
3 A rocky or uneven bottom or a wreck produces
an irregular image with peaks and troughs.
The dark layers indicate a good echo; the lighter
areas indicate weaker echoes. This could mean that
the upper layer is soft and therefore allowing sound
waves to pass to the more solid layer below.
It is also possible that the sound waves are making
two complete trips – hitting the bottom, bouncing off
the vessel, then reecting off the bottom again. This
can happen if the water is shallow or the bottom is
hard.
Factors inuencing the sonar display
The quality and accuracy of the display can be
inuenced by a number of factors including vessel
speed, depth, object size, background noise and
transducer frequency.
Vessel speed
The shape of the target changes along with your
speed. Slower speeds return atter, more horizontal
marks. Higher speeds cause the target to thicken
and arch slightly, until at fast speeds the mark
resembles a double vertical line.
Target depth
The closer the target to the surface, the larger the
mark on screen.
Water depth
As water depth increases signal strength decreases,
resulting in a lighter onscreen image of the bottom.
Sonar (Fishnder) application
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