How do you measure the height of a wave?

[Farmer Piles]

If you want real time and historic wave heights go to Magic Seaweed. It is a surf website but it has all the wave and swell charts from the NOAA and the remote wavebuoys.

Wave Buoys & Weather Stations

Looe Bay - Live Wave Buoy - Magicseaweed

UK & Ireland Charts - Magicseaweed

UK & Ireland Charts - Magicseaweed

Not only can you see what's going on out there and what is forecast, but you can look back at the historic and see what you were out in for reference. I use it a lot for both surfing and boating. Expand the map for the whole of the British Isles on the buoys.

 

[snowbird30ds]

Or in really extreme conditions, football pitches.

But height of a football pitch depends on when the grass was last cut.

 

[fisherman]

Seven stones lightship
NDBC - Station 62107 Recent Data

 

[Daydream believer]

I tried a couple of times to catch the right moment but kept missing it. This 45 ft boat went so deep into the trough ahead that several times his lower spreaders were hidden from my view. The wind was so light that we had to motor out of Camaret & were half way to the Chenal Du Four. Yet the swell coming into the Rade was enormous. We just motored up & over it with no ill effect.

 

[GHA]

If you want real time and historic wave heights go to Magic Seaweed. It is a surf website but it has all the wave and swell charts from the NOAA and the remote wavebuoys.

Wave Buoys & Weather Stations

Looe Bay - Live Wave Buoy - Magicseaweed

UK & Ireland Charts - Magicseaweed

UK & Ireland Charts - Magicseaweed

Not only can you see what's going on out there and what is forecast, but you can look back at the historic and see what you were out in for reference. I use it a lot for both surfing and boating. Expand the map for the whole of the British Isles on the buoys.

windy is good as well, graphs of actual ships/shore station data against forecast.

 

[coopec]

Height of "a" wave can only be guessed/estimated/measured by a human observer specifically there in that specific moment (let aside remote measurements), after a transient period that specific wave will disappear and no one else will ever meet her again. So yes anyone can say I have seen a wave Xm high.

Sorry! I disagree.

Sometimes you have absolute proof of the height of the wave.

"On 11 March 1861 at midday the lighthouse on Eagle Island,[5] off the west coast of Ireland was struck by a large wave that smashed 23 panes, washing some of the lamps down the stairs and damaging the reflectors with broken glass beyond repair. In order to damage the uppermost portion of the lighthouse, water would have had to surmount a seaside cliff measuring 40 m (130 ft) and a further 26 m (85 ft) of lighthouse structure. "

 

[mattonthesea]

I tried a couple of times to catch the right moment but kept missing it. This 45 ft boat went so deep into the trough ahead that several times his lower spreaders were hidden from my view. The wind was so light that we had to motor out of Camaret & were half way to the Chenal Du Four. Yet the swell coming into the Rade was enormous. We just motored up & over it with no ill effect.View attachment 154063

Three quarters of the way across the Atlantic westbound and with a weeks worth of steady F6(7) the waves had built to smooth and high. With no reference point I had no idea how high, except for the wavelength, until a cargo ship appeared on the horizon. It would only reappear every minute of so when we were both on the wave crests. But when it did it was tiny in comparison to the wave it was on.
As I hadn't seen anything that wasn't sea or sky for the last fortnight, I was fascinated by it.

 

[capnsensible]

I do what everyone else does. Think of a figure that might just correspond with the wave height, then double it.

Whatever someone tells you they've just been out in, half it.

 

[Biggles Wader]

But height of a football pitch depends on when the grass was last cut.

And then someone moves the goalposts.

 

[fisherman]

And then someone moves the goalposts.

....or indeed, the whole pitch.....

 

[Biggles Wader]

....or indeed, the whole pitch.....

If they had spent that sort of money on a team they might win something.

 

[fisherman]

If they had spent that sort of money on a team they might win something.

They can at least pull the ground from under their feet if they are losing.

 

[Stemar]

We took Jissel, our 24ft Snapdragon down the Western Solent, going with a spring tide and dead against a lively breeze. Lovely sunny day with a few cotton wool clouds, just a fun roller coaster ride. Then Madame looked behind and told me to look too. Standing in the cockpit with eye level around 6' above the water, we were looking up at our dinghy towed behind us. Quite steeply up. I'd estimate those waves at around 8-9ft high. What made it really interesting was the short wavelength. I've been in a swell of the same height, but with probably 20X the wavelength and it was hardly noticeable

 

[ean_p]

Well being a single hander & having sailed in fog for hours without sleep, I have seen my late grandad & Elvis Presley pushing a supermarket trolley. But I am b..gered if I have seen a double decker bus in the middle of the English Channel. So how on earth is one going find one out at sea to measure a wave with that system.

they turn up everywhere.......

 

[johnalison]

The most open sea I have sailed in was the Celtic sea on one return trip. There was a slight swell but the only rough F6-y bit happened at night, so I never got to see what it was like. On the other hand, I saw a friend's Sadler 32 hull disappear totally behind a wave just off Bradwell power station.

 

[The Q]

6 inches, normal there's a hire boat speeding past,
1 ft it's a bit windy,
Decks wet,(2ft above water line) it's very windy.
Any more than that, I'm in the bar.

Yep I gave up sea sailing some years ago.

 

[Farmer Piles]

I over heard a great conversation last year. Two old friends who hadn't seen each other for a while. One asked if the other was enjoying his boat and the reply made me smile.
"We don't go out if it's windy, we don't go out if it's wet, we don't go out if there are waves and we don't go out if it's dark. In fact, we don't go out very much at all."

 

[Roberto]

Sometimes you have absolute proof of the height of the wave.

I do not know the specific place, but the height reached by water is not a proof of wave height, a powerful wave against a large obstacle can send its water several times higher than its own height.

Beautiful images of tall lighthouses disappearing into water/spray

 

[andsarkit]

Oil rigs provide a perfect platform for measuring wave heights. I have fitted several RADAC systems to rigs for environmental monitoring. With 3 sensors in a triangle it is also possible to measure wave direction.
Many years ago I was involved in wavebuoys that use an vertical accelerometer. The acceleration is double integrated to give displacement. The results were not brilliant using analogue electronics for the processing but I expect modern accelerometers and DSP would give much better results. Someone needs to develop an app so you could use your phone accelerometer to do this.

 

[GHA]

but I expect modern accelerometers and DSP would give much better results. Someone needs to develop an app so you could use your phone accelerometer to do this.

Yet to use in anger but I use one of these for a DIY autopilot. All the data gets stored to an influxdb database once per second so will be interesting to see if anything useful will show up graphing the data
ICM20948 9DoF Motion Sensor Breakout