Wave Hights

[gandy]

Re: Root Mean Square

Could you give a worked example.. Say the blue arrow is 2ft from the middle, and the red one 3ft, then what's the significant wave height?

I saw the reference from Ships Cat saying it's peak-to-trough, and I'm not sure if this RMS stuff supports or contradicts that.

Tony S

<hr width=100% size=1>

 

[kindredspirit]

Re: Root Mean Square

This any help?

<A target="_blank" HREF=http://www.begleys.com/weather.htm>Useful links for Irish waters.

 

[gonfishing]

Real time wave height

Hi Haydn
Have a look here <A target="_blank" HREF=http://www.cefas.co.uk/wavenet>http://www.cefas.co.uk/wavenet</A>

Julian

<hr width=100% size=1>

 

[benjenbav]

Re: How big is this one?

I've thought about this all day and I reckon it's about 70 feet, give or take

<hr width=100% size=1>

 

[Ships_Cat]

Re: National Geographic definition + game

You put it much more eloquently than me - full marks. Even cats know it is peak to trough, seems to take a while for that to sink into humans' much smaller brains though /forums/images/icons/smile.gif.

John

<hr width=100% size=1>I am the cat but I am only 6.

 

[Ships_Cat]

Re: Root Mean Square

As another has said waveriders work out wave height from heave which is positive and negative - so they use an algorithm using the root mean square of those to get significant wave height. However, significant wave height is correctly defined as being the average height of the highest one third of the waves.

When people estimate the height of waves they tend to estimate a height that is close to the significant wave height ie they make an estimate that is higher than the average wave height so significant wave height is a useful observational measure for vessel management. Commercial vessels will normally have a wave height vs speed operating profile and for high speed craft that will normally be displayed as a graph in the wheelhouse/bridge.

As an example some fast vessels I am currently involved with can operate in 2m significant wave height for all speeds up to 19 knots, but then then the allowable significant wave height reduces until at 33 knots it is 0.5 m.

As said, wave height is definitely measured from trough to crest and the significant wave height is also worked about the trough to crest height. There is absolutely no question about that at all.

John

<hr width=100% size=1>I am the cat but I am only 6.

 

[longjohnsilver]

Take note yer pillock

We've been thru this loads of times, H00 has the correct answer, but I expect you knew that anyway!

<hr width=100% size=1>

 

[BrendanS]

Re: National Geographic definition + game

Here kiity!

Mind the Cat traps! /forums/images/icons/laugh.gif

<hr width=100% size=1>Me transmitte sursum, caledoni

 

[Ships_Cat]

Re: National Geographic definition + game

I just want a sardine or two and a saucer of milk but no one is giving them out /forums/images/icons/smile.gif.

Have you ever admired the waves in the saucer when the milk gets lapped up? - very pretty but your eyes have to be about 2 inches away to appreciate them cos then they look ginormus.

John

<hr width=100% size=1>I am the cat but I am only 6.

 

[KevB]

Look no further. The definitive answer

Is <A target="_blank" HREF=http://www.ask.co.uk/ix.asp?q=how+are+the+height+of+waves+measured&ac=none&xx=0&qid=263CE3D022F66E4DAF9E51D3CFEE2783&p=1&s=1&sp=ix&fn=tuk&b=0&fo=2&r=10&io=3&fp=3&fr=1&url=http://www.soc.soton.ac.uk/JRD/SCHOOL/eq/eq001a_wave01.html&adurl=> HERE. </A> All explained with nice animation..... Even I can understand this site!!/forums/images/icons/cool.gif

<hr width=100% size=1><A target="_blank" HREF=http://static.photobox.co.uk/public/images/45/99/10714599.s.jpg?ch=97&rr=16:00:39>Nirvana</A>

 

[KevB]

Re: Look no further. The definitive answer

Wave Amplitude=Maximum displacement from the mean sea level (sea level plus the top or bottom half of the wave/trough)

Wave Height=Trough to crest.


<hr width=100% size=1><A target="_blank" HREF=http://static.photobox.co.uk/public/images/45/99/10714599.s.jpg?ch=97&rr=16:00:39>Nirvana</A>

 

[Ships_Cat]

Re: Look no further. The definitive answer

That is a pretty good link - can I eat the fish when he's finished with the skipping rope /forums/images/icons/smile.gif?

John

<hr width=100% size=1>I am the cat but I am only 6.

 

[Bejasus]

Haydn...........a simple question

Why did you ask about wave heights?



<hr width=100% size=1>

 

[whisper]

Re: Haydn...........a simple question

Cos he's worried that this breezy weather might blow him over onto the towpath.

<hr width=100% size=1>