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How can i measure sea wave hight

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by Stuee123, Nov 30, 2017.

  1. Stuee123

    Stuee123 New Member

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    Hi, im messing with Raspberry pi and want to measure sea weather height for tide, swell and waves.
    I want to mount it on a channel marker and it to be solar and transmit via 4g internet, which i have covered.
    Im struggling to find a solution to measure the water conditions. I can work the software for the reading so that doesnt bother me, but how can i measure from the station (prob 5m above highest tide.
    The tides vary from 0.3m to 4.6m, swell isnt huge, probably 1-2m max and tha same for waves. prop 1-2m max.

    Ive looked at ultrasonic but max for that is 7m.
    i also thought about a tube with a float inside it so it moved up and down and a laser at the top, downside with that the crustations etc will grow in the tube and stop it working.
    another idea have a ball with a pressure regulator on it and tethered near by, as the swell goes up and down the pressure changes and sends that to the rpi, only issue with that is how accurate is it really?

    So any suggestions. I do like the ball idea because i can add a current wheel and a water temp to the underside of it for extra data.
    I look forward to seeing some replied :)
     
  2. dr pepper

    dr pepper Well-Known Member Most Helpful Member

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    You can get hi res pressure sensors that can tell small changes in altitude, that would give more of a change in height rather than an exact level.
    Another question was asked like this not so long back, might be worth looking for it and see what they did.
     
  3. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi 123,
    If you want to measure the true tidal height you must include the ambient atmospheric pressure, local air weather pressure will effect the apparent tidal height.

    This is normally done using a submerged differential pressure transducer.
    The connecting cable to the transducer has an inbuilt air pipe, so the transducer auto corrects for ambient air pressure.

    Swell can be measured using a low cost XYZ accelerometer modules from China.

    Wave height and energy can be little tricky to measure.

    E
     
  4. dave

    Dave New Member

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  5. cowboybob

    cowboybob Well-Known Member Most Helpful Member

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    You (I'm assuming you were "stuee" then) posted this identical question on Sept. 21st.

    The suggestions offered at that time are still valid. Nothing much has changed since then.

    I don't know where you live, but I might point out that channel markers are generally (in the US) controlled by the US Coast Guard and the Army Corps of Engineers. They don't take kindly to civilians mounting anything on their towers. If they find such items, they ordinarily simply remove them and pitch them in the trash.

    That said, have you investigated/tried any of the measuring methods proposed? Your question does not suggest that you have.

    (If you are not the poster of Sept, 21st, my apologies. But my 3rd paragraph is still relevant).
     
    Last edited: Nov 30, 2017
  6. Externet

    Externet Member

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  7. dknguyen

    dknguyen Well-Known Member

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    I think the most elegant solution is a pressure sensor sitting on the bottom that will measure the pressure of the water above it. Water is quite heavy and of more consistent density so I would think it would be quite accurate (definitely more accurate than doing than a pressure altimeter). I would be more concerned about whether it only responds to widespread depth changes like tides and not localized depth changes like those in waves. waves. It seems simple enough that it's worth building one to test to see if it works. It would be the most mechanically rugged, simple, and elegant solution. Might want a temperature sensor in there to adjust for water density.

    The method that first jumped into my mind is basically your ball in a tube method (in my mind it was a float enclosed within a guide rail and it used a coiled tether distance gauge anchored on the bottom rather than a contactless distance measurement.)
     
    Last edited: Nov 30, 2017
  8. atferrari

    atferrari Well-Known Member

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    Hola Eric,

    From your measurements, how could you tell waves from swell? Just based on period? In doubt myself. ??
     
  9. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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  10. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hola,
    My equipment for hydro-graphic survey vessels, used onboard XYZ accelerometers to measure the vessel 'heave' which was used to correct the echo sounder readings.
    As you say it was based on the typical swell period rates.
    For wave height and wave energy we used submerged fast response tide gauge pressure sensors for the higher frequency wave heights.

    I owned company that designed and manufactured all sorts of hydro and land based survey equipment for UK and international companies, for about 25 years.

    Eric
     
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