What are carriage requirements of Echo Sounder ?

As per SOLAS CH V / Regulation 19,  

All ships of 300 gross tonnage and upwards and passenger ships irrespective of size shall be fitted with, an echo sounding device, or other electronic means, to measure and display the available depth of water.

Principle of Echo Sounder: –

• Echo sounder measures the depth of water by measuring the time for a pulse of energy to travel to the sea bed and back and work on the principle of reflection of acoustic energy.
• Short pulse of sound energy is transmitted vertically down from the ship.
• This pulse having been reflected from the sea bottom returns to the ship in the form of an echo.
• Travel time (t) taken for its return, depends upon the depth of water (d), and on the velocity of sound (v) through the water.
• Time taken (t) = (2 x d) / v or d = (v x t)/2

Performance of an echo sounder system depends on the accuracy with which the velocity of source propagation is measured.