Exam 1 Flashcards
Doppler speed log
registers a change in frequency between the transmitted signal and the received signal and then calculates the velocity of the vessel based on the frequency shift
Echo sounding is a type of?
Sound Navigation and Ranging (SONAR)
Echo sounding is used to?
determine the depth of the water by transmitting sound pulses into water
Fathometer indicates the depth of water where?
under keel or where the transducer is located
Fathometer is dependent on both?
specular (direct) and diffuse (reflection at an angle) reflection
Range of fathometer is?
0 to 4,500 feet
Fathometers emit how many pulses per minute?
10 to 600 pulses per minute
Speed of sound through water is approximately?
4,800 feet per second
You should always know your _________s location.
Fathometer
What does a Oscillator do?
creates electrical signal at the desired frequency
What does a Transducer do?
converts electrical signal into ultrasonic vibrations for transmission. Also converts the return echo back into an electrical signal
Name two types of Transducers?
Electrostrictive and Magnetostrictive
types
It is essential the user select the _____ depth soundings on the depth sounder as the navigational chart in use.
SAME
Gain: the ____ the bottom, the less gain (sensitivity) required
harder
Define Bathymetric Navigation?
The method of navigating by using a fathometer
Speed Log is used to determine the vessels _____.
Velocity
Name three different Speed Logs?
- Patent logs: Small tubular finned device attached to the end of the drag line that would spin as the vessel moved through the water
- Pitot-static (pitometerlog): based on principle of comparative measurements between static and dynamic pressured in a pilot tube extending from a vessel’s hull
- Impeller log: electromagnetic device which used a small propeller spun by water which was then converted to an electrical signal
Modern Speed Logs are?
Electromagnetic or doppler
Define the Doppler Speed Log, Doppler Effect:
Shift in frequency between a transmitted and received signal caused by the motion of a vessel over bottom or through water
The Doppler Speed Log receives what through the water?
reflected signal from particles suspended in water.
True or False: The Doppler Speed Log registers change in frequency, not time, to measure speed
True
The speed of sound through ocean water is nearly always __________.
faster than the speed of calibration for the fathometer