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# Electronics/Marine instrument.

Question
QUESTION: Dear ZZ

Which Marine instrument can be useful for measuring the ocean or sea height or depth?.

Thanks
Prashant

ANSWER: There are many instruments at different levels of sophistication and features. Here, below is a listing of some of the variations and types of equipment employed:

http://www.vaisala.com/en/maritime/Pages/default.aspx?gclid=CPCIn-CwrscCFQwyaQod

More specifically, here are some depth measuring instruments:

and further:

https://en.wikipedia.org/wiki/CTD_(instrument)

The typical depth measuring apparatus works by knowing the speed of sound in water and sending a sonic signal down to the bottom and measuring the time it takes to reflect back to the observation station on the vessel thus allowing for the calculation, quite precisely, of the depth.

Other methods can use electronic signals to do the same type of measurement.

And, of course the early mariners used a rope with knots in it and a heavy anchor on the descending end thus giving the depth by observing how many knots went down when the anchor hits bottom.

Measuring wave heights is explained here:

http://magicseaweed.com/help/surf-forecasting-basics/measuring-wave-heights

There are two most common methods and are often used in combination.

http://magicseaweed.com/help/surf-forecasting-basics/measuring-wave-heights

http://www.surfertoday.com/surfing/8357-how-to-measure-wave-height-in-surfing

The Hawaiian scale and Bascom Method are explained above.

Big vessels in rough water use different methods from those above - which are more for surfers and recreation oriented applications.  Here below is a description of how larger boats deal with large waves in their region:

https://en.wikipedia.org/wiki/Wave_height

Hoping you can get the information you want from the above references; if not please send follow up question.

---------- FOLLOW-UP ----------

QUESTION: Dear ZZ

Thanks.

I wanted to know How deep
is the Pacific ocean, Antartic ocean, Indian ocean.

Thanks & Regards,
Prashant S Akerkar

ANSWER: The Pacific Ocean deepest point is about 11,000 meters or 36,000 feet.

https://en.wikipedia.org/wiki/Pacific_Ocean

The Antarctic ocean also knows as the Southern ocean has a maximum depth of 7,200 meters or 24,000 feet.

https://en.wikipedia.org/wiki/Southern_Ocean

The Indian ocean has maximum depth of 7,906 m (25,938 ft).

https://en.wikipedia.org/wiki/Indian_Ocean

Realizing, of course, the bottom of the ocean is not flat and the depth varies greatly from place to place.

Hope this helps.

---------- FOLLOW-UP ----------

QUESTION: Dear ZZ

Thanks.

The depth of the oceans mentioned in the
Wikipedia must be measured by Marine instruments.

What will be the Marine instruments and the techniques, principles behind the measurements?.

Thanks
Prashant

The ocean depths figures from the wiki pages is likely a consensus figure from the many such measurements that have been taken over the years with various instruments in use at the time taken.  I think the most common measuring methods are the sonar ping to the bottom and back by taking the time of the return pulse then dividing by 2 to get the distance to the bottom.

The distance is not always measured at the exact same spot as the ocean is a big place and the underwater mountains, hills and valleys make it impossible to always take the measurement from the very exact same spot.  While the measuring technique is quite precise, the location for the measurement is not.

I think most recently, techniques using what is called a bathymeter may be used.  It differs in that it uses an array of solar pings covering a wide area of the bottom surface allowing a kind of mapping output.

https://en.wikipedia.org/wiki/Bathymetry

Mapping the ocean floor is of interest in the study of underwater currents and motions around the underwater landscape.  These are important data points for navigators, weather forecasters, commercial ocean travel and so forth.

Happy day to you.

Electronics

Volunteer

#### ZZ

##### Expertise

Electronics questions about AC, DC and digital theory.

##### Experience

Graduate electrical engineer with over 40 years in electronic design, manufacturing, project organization and patent review. Experience in fields of industrial and consumer electronics (audio, video, acoustics, etc.)

Organizations
IEEE (Institute of Electrical and Electronics Engineers); Senior Life member AES (Audio Engineering Society), Fellow Life member

Education/Credentials
BSEE University of North Dakota