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HOW TO DISTINGUISH THE NATURE OF BOTTOM
• There are different natures of bottom such as rock, sand, mud or etc.
In case you distinguish the nature of bottom, you judge from the thickness of bottom image and the situation
of second reflection. At the hard bottom like rock, reflection of transmitted wave becomes strong and bottom
image becomes thick and the second reflection becomes easily to appear. On the other hand, at the soft
bottom like sand or mud the reflection becomes weak and bottom image becomes thin and the second
reflection becomes hard to appear.
*Second reflection .......... Ultrasonic wave transmitted from transducer is reflected from sea bottom and
then it is reflected from both sea surface and bottom finally. In short, second re-
flection is image of two round-trips between sea surface and bottom.
Rock
Sand or mud
Second reflection
