Question

Write two points related to Echosounder.

Hint:

Think about what the instrument measures and what danger it helps to avoid.

Answer 1

Step 1: Understanding the Concept:
An echosounder is a navigational instrument on board a ship. It sends a sound pulse down into the water and listens for the echo that returns from the sea bed.

Step 2: Point 1: What it does:
It is an instrument by which the depth of the water can be measured below the keel of the ship. The keel is the lowest part of the ship, so this tells the crew how much water is left under the ship.

Step 3: Point 2: Why it is used:
This helps us to prevent the ship from grounding. If the depth reading falls dangerously low, the officer can change course in time.

Final Answer:
An echosounder measures the water depth below the keel and helps prevent grounding. \[\boxed{\text{Depth below keel; prevents grounding}}\]