Question

explain the significance of ensuring that the echo sounder always provide correct and reliable informaion?

Answer 1

Echo-sounders transmit a pulse of acoustic energy down towards the seabed and measure the total time taken for it to travel through the water, i.e. the outwards and return journey. If the measured time is one second and it is known that the speed of acoustic waves is 1500 m/s, the depth is obviously (1500 x 1)/2 metres = 750 m.

By using a recorder with slowly moving paper to display the time of transmission and then the echoes as they return, a past history of the depth and of the sea bed topography is built up. If the system is sufficiently sensitive it will also display the echoes from fish, but this gives merely an indication of their relative abundance. Instruments capable of making quantitative acoustic measurements are needed, together with methods of turning these into figures of the absolute fish abundance. To do this, echo-sounders with precise characteristics have evolved. Their signals are coupled to a specially developed instrument, the echo-integrator, which selects and processes them in various ways. In this section we first consider the echo-sounder.

Answer 2

Significance of ensuring that the echo sounder always provide correct and reliable information:

• Echo sounder is a component used to measure the depth of water.
• The echo sounder with the transducer transmits the sound pulses downward into the water.
• The echo sounder receives the echo reflected from the bed.
• The depth of water is estimated by the time interval between the emission of the sound pulse and its return as an echo.
• The double way transit time of an acoustic beam that has been reflected from the sea bed is measured by all the vessels fitted with single beam echo sounder.
• A continuous profile of the reservoir bed is recorded by the echo sounder.
• The echo sounder is accurate with accuracy of the order of several cm can be obtained.
• High accuracy is provided by the Dual frequency echo sounder.
• Accuracy is high particularly in case of soft reservoir bed.
• Later resolution of the echo sounder depends on the depth of the water.

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