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Author: Subject: Measuring Waves
Thodd
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posted on 10-5-2004 at 09:16 Reply With Quote
You've got me there Airborne!

I've never seen or heard of a duck dive like that before!

Personally when I'm paddling out I like to power up the face of the wave if I can, if you time it right the "suck" of the wave before it breaks will shoot you in the air and you can do a fancy 360 spin.... its completley pointless but its an amusing thing to do while your swiming out!


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Airborne
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posted on 12-5-2004 at 19:02 Reply With Quote
interessting idea! I also like to go over the wave.






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posted on 15-5-2004 at 19:11 Reply With Quote
Just to go back to measuring waves:

quote:
Originally posted by Thodd
I've always thought that waves were measured from the back? Isn't it something to do with forcasting the swell?
ie... waves out in the sea don't break because the water they are in is to deep... so it could be said that it they don't have a face and both front and back are the same size. When the Bouys are bobbing up and down sending all that scientific data back to scientific places it is that size that they record.
"



Buoy measurements out at sea are swell height, and Thod is almost right as to back and front being the same. There is some small difference.

Swell height is not the actual wave height when these break. Swells are measured out at sea and the height stated (spectral height, effective height or something like that) is the maximum height acheived by the smallest two thirds of the waves of a swell (something to do with energy measurements, etc.).

So once the swell is forced on to a shallow shelf over a short distance the height of the wave may be increased. If it travels over a long softly sloping bottom the wave will lose energy (and height) as it travels along, and in some cases it may never break until it impacts onto a cliff face. So the correct measure of a "ridden wave" should be its face height of the wave in question.

You then go on to measuring real height (straight up) or along the face (join the top and the bottom with a straight line, and measure the line). The latter done with many big waves as it gives more of an idea of how thick it is.





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Airborne
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posted on 16-5-2004 at 18:40 Reply With Quote
WOAH! So much info....i sort of get it. Doesn't a waves height also depend on how far the "fetch" is. This is geography GCSE by the way. The "fetch" is the length of water over which wind has blown.

There are two types of wave:
1) Constructive wave - this is a wave which is long in relation to height, it's gentle, is less erosive and is a making wave. By the word "making i mean it carries the sediment/material up to the beach and deposits it, this makes or adds to the amount of material eg. sand on the beack, making it larger. Hence the name "constructive" wave. These waves break on an average of 6-9 per minute.

2) Destructive wave - this is a wave which is high in proportion to length, it is more powerful and more erosive. Instead of "making" it "destroys" by carrying sand and pebbles out to sea, away from the beach. It is powerful so it also errodes cliffs and beaches. Hence the name "destructive" wave. These waves break on an average of 11-15 per minute.

"Swash" is the force of a wave coming towards the beach and "Backwash" is the force of the wave retreating away from the beach. Like a wave motion when it laps up the sand and then retreats again.

In a Constructive wave the swash is greater than the backwash. Therefore if there is less backwash then the lip of a wave won't form because there is still water underneath the lip. In other words the water underneath the unformed lip hasn't been taken away with the backwash leaving an overhanging lip because the backwash is weak.

In a Destructive wave it is the exact opposite. The backwash is greater than the swash. Therefore a lip is formed and the wave becomes a tall breaker. It breaks downwards with power and force.






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posted on 12-5-2005 at 10:44 Reply With Quote
airbone where did that crap about how we measure waves in aus come from? everyone in aus measures in ft and usually the majority of surfers in aus talk down the size which i have been brought up to do and for example a wave with a 5ft face which u guys have been saying is 2-3ft would be in the 1-2ft caterogry in my book and a 6ft wave would have around 12ft plus face. and a 'blow out' is when a wave barrells quickly n heavily and all air inside barrell gets spat out, messy surf is refered to as blown out.
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posted on 23-5-2005 at 18:45 Reply With Quote
lol, calm mate
i just heard that from one of the other members on the forum...i think, it was ages ago i cant even remember talking about it...ure right about the blow out, blown out part i must have made a spelling mistake and missed off the "n", weird how you look at waves as smaller, i dont really see any point






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posted on 26-5-2005 at 08:16 Reply With Quote
Surely 1 foot = 12 inch. So how can a wave be smaller than it actually is? ie our 2-3ft wave is your 1-2ft wave?

Somewhere between England and Australia we've lost 12 inchs! Maybe the lost inches stopped off at Singapore and missed the connecting flight!






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posted on 26-5-2005 at 11:38 Reply With Quote
lol, thats a good point Thodd

and when you think about it 12 inches is around 30cm...so when you hear 2-3 foot they're only 90cm tall, that's 3x30cm rulers...so when you look at it, its not very tall at all, about the height of my desk. But when you hear someone say "3ft tall waves" i seem to think people think its bigger than it actually is. Dont know about making it smaller or not now.






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posted on 26-5-2005 at 16:03 Reply With Quote
I always measure waves by the face.

I thought measuring from the back was 'Hawaiian Style'.

But I have developed my own wave measurement system which takes away the confusion of ft/ metres & front/ back.

It goes like this.

Level 1 - Bugger, it's flat - if I'm desperate I'll get my skimboard out
Level 2 - Am I really that desperate?
Level 3 - Spose it's worth getting suited up
Level 4 - Fun
Level 5 - Superfun
Level 6 - Occasional anxiety
Level 7 - Pushing the envelope
Level 8 - I'm sure it wasn't this big when I paddled out!
Level 9 - Screw that, I aint going out in that
Level 10 - I'm afraid to park my car here in case it gets washed away!!

This usually clears up the confusion!!

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posted on 26-5-2005 at 16:06 Reply With Quote
Ah, I appear to have repeated myself a little!!

Ooops sorry!





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posted on 26-5-2005 at 16:15 Reply With Quote
all this talk of measurements
bit like my dick , depends who you ask !
you,ll get various opinions on how big it actually is,
i,d say ots huge
er indoors tweeny

and if you measure it from the back , wey ho







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Thodd
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posted on 27-5-2005 at 09:54 Reply With Quote
i'm gonna use sinista's scale from now on.
its much easier.





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Airborne
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posted on 27-5-2005 at 18:04 Reply With Quote
yeh great idea there sinister






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posted on 28-5-2005 at 04:56 Reply With Quote
quote:
Originally posted by kelvin
all this talk of measurements
bit like my dick , depends who you ask !
you,ll get various opinions on how big it actually is,
i,d say ots huge
er indoors tweeny

and if you measure it from the back , wey ho




If I try measuring from the back the wave usually closes out... It's certainly rare for me to tuck into a nice little barrel anyway! But my backside 0ff-the-lip re-entries are pretty good!



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Airborne
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posted on 28-5-2005 at 11:46 Reply With Quote
lol!

whatever Al

Lets get back to the real subject of this topic. Hehe, I was browsing in the Stormrider Guide Europe and saw this at the front:

Wave face measurements:

huge: 10+m (30+ ft)

triple overhead: 6m (18 ft)

double overhead: 4m (12 ft)

head high and a half: 3m (8ft)

head high: 2m (6ft)

chest high: 1.5m (4ft)

waist high: 1m (3ft)

knee high: 0.5 (2ft)

double over ankle: 0.3m (1ft)

flat: 0m (0ft)

Although this is less fun than Sinisters way, i think its pretty clear and acceptable.

Airborne.






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posted on 16-6-2005 at 10:30 Reply With Quote
no way that is correct, so according to that on tuesday i pulled into a 5m closeout?? reports over here were calling it 8ft+ and face of the wave was around 10-15ft, easily biggest swell ive surfed, but no way i would call it 5m more like 5-6ft (5 because of inconsistency), i think i might talk it down abit mainly because i dont wanna sound like a full blown kook saying i surfed 5m. everyone over here seems to talk it down heaps, dunno why ey.

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posted on 16-6-2005 at 11:45 Reply With Quote
LOL! what measurements are using over there in Oz??

5m is tall you know, on www.onlineconversion.com it says 5m = 16 ft...those measurements are scientifically correct, so either Europes measurements are different to yours, or your surfers may be a bit confused.

So the waves you surfed were most likely 5 metres tall, but all this comes down to how u measure it again, back to where we started.






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posted on 18-6-2005 at 03:58 Reply With Quote
airborne the face height of the wave is not how u call wave size.
how big would u fellas call this wave of parko getting slotted off his tit on tuesday??
[IMG]http://img163.echo.cx/img163/2815/14jun006big5xc.jpg[/IMG]

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Airborne
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posted on 18-6-2005 at 09:11 Reply With Quote
This is what we've been discussing all this topic, earlier i posted this:

"Now, we move on to how to measure waves:
Basically, there are 4 ways that I've learned to measure waves, and that depends on where you are in the world.
East coast USA: Waves are measured using body parts until it gets overhead. Example: It's knee high, stomach high, thigh high, chest high, etc.
West coast USA: Also use body parts, though not as detailed as east coast. West coasters don't use "thigh high", or "stomach high". Face height is typically used to measure waves, the wave's rideable face from trough to crest. Therefore, with an average man being close to 6 feet tall, a head high wave is 6 feet.
Hawaii: 1/2 the face height. Not sure why this is done, but that's just how they do it. There's alot of theories as to why, but who knows. A head high wave in Hawaii is 3 feet.
Australia: These guys have the weirdest method that has been described to me by my Aussie friends as measured by "the powerful part of the wave". So, for example, a mushy head high wave to an Aussie would be about 3 feet, but a top-to-bottom barreling head high wave might be 5 feet. Neither measurement is accurate technically, but that's how they do it. Plus, they measure the swell height in meters anyway."

That was from an article somewhere...its funny how Australia has the weirdest method I measure wave height by the face size anyway because:

1) its the part that everyone sees
2) you dont have to add on the depth of the water if anyone does that anyway
3) doesnt really include measurement of power

Having said that, i admit i am rubbish at looking at a waves and saying how tall it is. But looking at your picture i would say "judging by the height of those surfers, and the average man being around 6ft i would say that wave face is 10ft where the lip is breaking" lol i might be completly wrong...but then everyone has their own method. Your right, most people might not measure it by face height, me and my friends might be the only ones that do lol.

Judging from the article Aus and UK sound different methods.

Keep posting all.

[Edited on 18-6-2005 by Airborne]

[Edited on 18-6-2005 by Airborne]






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posted on 25-7-2005 at 02:35 Reply With Quote
i came across this text from ben matson a local surf forecaster here about measuring waves

Imperial measurements (ie feet) are much easier to use when speaking about the surf, as it rolls off the tongue a lot better - especially as waves are rarely at convenient metric intervals like 1m, 1.5, 2m.

For example, when was the last time you heard someone coming out of the surf at Snapper, frothing about how there were "absolutely sick one point two five metre barrels"? It's much easier to say that it was "four foot and pumping".

As for how waves are measured.. it's been discussed in these forums (and many others) a million times before. I don't think it really matters at all whether everyone agrees or not. The key point as far (as surf reporting is concerned) is the swell trend and the consistency of the reporter. If someone said that it was 4' today and then they reckon that it's 6' today, then it must be bigger. It's up to you to work out to what degree it has increased - but the most important facor is the swell trend (up, down, weaker, stronger).

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