Question

The instrument used to record the speed of the vessel based on the acoustic principles is

• A. Auto pilot
• B. Chromometers
• C. Doppler logs
• D. Patent logs

Hint:

Vessel Speed Instruments:
Acoustic Sound Principle = DOPPLER LOG.
Mechanical Rotator = Patent Log (Taffrail log).
Hydrodynamic Pitot Principle = Pitot Log.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Marine electronic navigation and hydroacoustic instrumentation: Doppler speed logs calculate vessel speed through water and over ground by measuring the Doppler frequency shift in transmitted ultrasonic sonar pings.
Key Formula or Approach:
\[ \Delta f = f_r - f_t = \frac{2 v \cdot f_t \cos \theta}{c} \quad \implies \quad v = \frac{c \cdot \Delta f}{2 f_t \cos \theta} \]

Step 2: Detailed Explanation:
In marine navigation instrumentation and vessel speed measurement:
1. Doppler Log (Acoustic Doppler Speed Log) (C): An electronic hydroacoustic navigation instrument that transmits high-frequency ultrasonic acoustic sound pulses into the water column and bottom. By measuring the Doppler frequency shift ($\Delta f$) of echoes reflected back from water scatterers or the seabed, it computes the precise Speed of the Vessel (both Speed Through Water [STW] and Speed Over Ground [SOG]).
2. Patent Log (Taffrail Log): Mechanical rotator towed behind the vessel.
3. Autopilot: Automated steering system.
4. Chronometer: High-precision timekeeping instrument for longitude determination.

Step 3: Final Answer:
Hence, the acoustic instrument is Doppler logs, matching option (C).