pods for primates : a catalogue of surfboards in australia since 1900
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surfresearch.com.au 
appendix : wave measurement
Willard Bascom : Estimating Breaking Wave Height
INTRODUCTION
Measuring wave height (a moving object constantly changing shape) has been a consistant discussion topic amoungst surfers.

John Kelly Jr.in Surf and Sea 1965, proposed  two ways of measuring waves - "you can over estimate or you can under estimate".

A basic scientific method was detailed by Willard Basom in his seminal work on wave research,
Waves and Beaches (1964).


DEFINITION
Breaking wave height is measured on the face, from sea level to the wave's maximum crest.

The face is measured because...
1. the action of the face causes errosive action to the bottom and the beach.
2. the action of the face impedes a surfers' progress out through the surf.
3. the face is the slope on which a surfer rides.

Measurerment taken from the shore allows...
1. fixed reference points.
2. confirmation by a second party.
3. measure of a maximum range
4. size and period to be measured from the beach for safety.


THE BASCOM METHOD

"Simply stand  on the beach face at such a level that the top of the breaker is exactly in line between your eye and the  horizon. Then, as shown in Figure 56 (below), the vertical distance between eye and  backrush curl (which is about the same as the average sea surface) is equal to the height of the breaker."

- Bascom : Waves and Beaches. Page 173.

BASCOM'S DIAGRAM

FIG. 56. When the observer's eye is aligned with the top of the breaker and the horizon,
the vertical distance between the eye and the backrush is equal to the height of the breaker.
Bascom : Waves and Beaches, Page 173


EXPANATORY NOTES
1. The Peak of the Wave (kulana nalu)
a. As a swell approaches the shore, friction with the bottom causes the  wave to become progressively  taller, reaching maximun height just before breaking.
In most situations the largest waves break furthest from the beach.
This illustrated by....
 
FIG. 53. The breaking of a wave :
1. Swell peaks up on entering very shallow water.
2. At depth equal to 1.3 times the wave height, it breaks.
3. Wave re-forms and breaks again.
4. Water moves beachward as wave of translation.
5. Finally rushes up the beach.
Bascom : Waves and Beaches, page 160

b. Most surfing waves, after breaking, maintain a peak profile with the maximum height in the crest. The shoulder is in deeper water and is smaller, behind the crest the wave is whitewater (nulu muku), transformed to a wave of translation, and is smaller.



Note that, for simplicity, the diagram above does not include the respective wave troughs.

c. Whatever the measured size of the wave, a surfer does may not always ride positioned at the wave's maximum size.
In the photograph below, at this point the wave is ...

largest for the red shorted surfer, smaller for yellow and smallest for blue.
Photograph : Australian National Travel Association
from Klein : Surfing, 1965, pages 176 and 177
Boardshorts by surfresearch.com.au
2. Back Rush Curl
The backrush curl or backrush wave is the small wave that finally breaks before the wash rushes up the beach.
This is an estimate of  the average sea level, as distinct from the extent of the wash which has a great variation.

3. The Horizon
In normal visibility the horizon is approximately 19 miles, a huge distance relative to wave height.

4. The Trough
The trough of a breaking wave is not the same as that of a deep water wave.
Apparently (more research required), as a wave approaches shallow water the oscillating wave rises above the average sea level, see Bascom's Diagram Figure 53 above, and the trough assumes different characteristics.
The trough of an idividual breaker is the sum of many complex factors and variation from one wave to the next may be extreme.
There is some argument as to whether surfers actually ride the trough of a breaker, see alt.surfingPost #4 and others, below.
Bascom's method does not measure the trough.

5. Some Surfing Exceptions
a. In  point surf,  the reflection of wave energy back from its point of original contact may cause the wave to peak at maximum height some time after first breaking.
In some extreme swell conditions at point surf, the further the surfer rides, the wave gets larger.
The maximum peak should be measured.
b. In some unusual situations waves inside the surf zone may combine to produce a lager wave than those breaking outside.
Surfing terminology : a double-up (huai)
These exceptions should be compensated for in the following discussion.


SOME PRACTICAL APPLICATIONS
1. Simple observations
Standing at the waters edge, If a set wave is below the horizon -it is under head high.
Standing at the waters edge, if a set wave obscues the horizon - it is over head high.
The further you have to move back and up, to align horizon and crest, the larger the waves are.

2. Familiarity
Regular use of a standard method at familiar locations means that size estimation becomes learnt.

3. Unknown surfing breaks
The use of a standard method is particually useful at unfamiliar locations.

4. Photography
Note that surfing photographs are rarely shot square to the wave face.
If shot from above , size will be under estimated.
If shot from below , size will be over estimated.

5. Other Wave Vaiables
All waves of the same height are not the same.
Each varies with shape, velocity and power...

a. Shape is principally determined by bottom shape and local wind conditions.

b. Wave velocity, that is the speed that the wave travels directlly towards the beach, is a product of the strength and duration of the formation winds.
Waves travel between approximately 20 and 40 knots in deep water (more research required),
slowing down as they enter shallower water.
Although waves with a faster velocity are obviously 'faster'; since surfers ideally slide across the face and not directly to the beach, wave velocity may not be as crucial as curl speed  (the rate of peel).

c. Wave power, also a product of the strength and duration of the formation winds, can be estimated by calculating the time between waves of a set.
For a given height, the longer duration between waves of a set, the more the power of the originating winds. (more research required)


AN HISTORICAL PERSPECTIVE
1. Ancients
Although ancient Hawaiian surfers had many words descriptive of surfing conditions, it does not appear that they used an empirical form of measurement. (more research required).

2. The 1900's
Obviously hard to substantiate from historical records, but all indications are that Duke Kahanamoku and Tom Blake measured their wave size from the face.
Duke Kahanamoku in World of Surfing, page 75  reports on surfing at Waikiki in 1930..
The Bluebirds facing me were easily thirty-plus waves....(my emphasis)
Tom Blake's Hawaiian Surfboard, pages 62 to 65, details the various breaks at Waikiki and their suitable sizes.
A photograph between pages 32 and 33, the famous Kalahuewehe Surf at Waikikii , identies a wave as about 30 ft.
All details correspond to what would be expected from measuring the face.

3. The 1940's
Often thereported heights of yesterday's waves were/are exaggerated.
A recuring theme in the "You should have been here yesterday!" syndrome.
Bob Simmons (?) proposed the 2 + 2 Rule : For any reported wave size, divide by 2 and add 2 feet.
(My emphasis and I can't find the reference for this, probably LEGENDARYSURFERS.com)

5. The 1950's
Big wave surfing was boosted with the development of fibreglassed boards with fins.
Increased interest in wave height saw Buzzy Trent propose a subjective method - Increments of Fear
Jonathan Hoag  (alt.surfing Post #40) reports Rabbit Kekai told me the height is measured from the back of the wave.

6. The 1960's
In Hawaii large wave surfing accelerates as the focus shifts from Mahaka to the North Shore - Sunset and Waimea
Jonathan Hoag (alt.surfing Post #40, 1996) contacted several surfers of the period and reported these comments ...
George Downing :If you're talking about height use the "dictionary's definition" of height, "vertical", i.e.vertical height of the face before it breaks, despite the fact that there is some addition of height because a wave sucks out some of the water in the trough.

Ricky Grigg : measure by the book (oceanography) - the height of the face, trough to crest.

Peter Cole : never has adjusted his scale downward.

Note : These three surfers have impecable big wave riding credentials.

The comment form Neal Miyake (alt.surfing, Post #23, 1996) may be a reasonable assessment...
In Hawaii, we "measure from the back," meaning, we essentially cut the wave face height in half.
The reason (I think) is because of Californians in the 50s and 60s sandbagging to surprise newcomers to the islands

7. Waves Buoys
Modern metorlogical forcasting incorporates deep water wave monitoring buoys that provide swell readings, ostensibly as a support to shipping as for protection of land exposed to wave damage.
As deep water wave buoy readings approximate estimations by the Hawaiian method (ie from the back), these readings were used as 'scientific' justification.

8. The 1990's
With a resurgence in surf media attention on big wave riding and the development of tow-in surfing that put a premium on large wave performance, some surfers around the world adopted the Hawaiian Method - that wave height be measured from the back.
Apart from the obvious technical inaccuracies, this favoured under-estimation as a badge of bravado.

9. Tow-Ins
The use of mechanical powered craft to assist boardriders catching waves pushed big wave riding to new extremes.
This adreline powered approach resulted in all rational estimations of wave size being ignored.
The mainstream surf media simply skirted the issue, publishing a series of  increasingly larger ridden waves reported as "bigger than the last ones".
The extent of confusion on the subject is illustrated in  Warshaw, Matt : Mavericks - The Story of Big Wave Surfing, 2000
Note : All the surfers referred to in this section have impecable surfriding credentials.


ALTERNATIVE METHODS
1. The "Hawaiian Method"
The "Hawaiian method" proposes that wave size be measured from the back.
It usually results in an estimation less than half that of a face measurement.
Coming into use during the 1960's, the 'Hawaiian method apparently was adopted as  pyhscological intimidation of inexperienced visitors, see histoical notes above.
This "method" was reinforced by the inceased use of wave buoys, whose measuements often equated the "Hawaiian method".
See below.
It gained some popular use in the 1990's with a resurgence in media attention on big wave riding and the development of tow-in surfing that put a premium on performance extremes.

Objections
1. The wave face is the slope on which a surfer rides and what impedes a surfers' progress out through the surf.
2. No fixed reference points.
3. Difficult to confirm by a second party.
4. Diffifcult to measure a maximum range -  if a wave has a face of 1 foot, how big is it from the back?
5. Questionable historical precedent, see above.
6. Favours under-estimation as a badge of bravado.

2. Wave Buoys
Modern metorlogical forcasting incorporates deep water wave monitoring buoys that provide swell readings, ostensibly as a support to shipping as for protection of land exposed to wave damage.

Objectons
1. Since these measure deep water waves only, the heights are conservative compared to wave heights attained before breaking.
2. The more rapid the change in bottom contour, the greater the difference between swell height and breaker height.
A given swell height recorded by wave buoys will produce different size breakers on different bottoms.
3. Wave buoys measure the oscillating wave, that is crest to trough. A breaker, by definition, is a collapsing oscillating wave.
4. Apparently (more research required), breakers rise above the average sea level, see Bascom's Diagram Figure 53 above.
5. Surfers generally ride the face of a breaker, crest (muku) to base (honua), not the trough.

3. The Surfer on the Wave
a. Wave size is calculated by comparison with the height of the rider by an observer.

Objections
1. Observer must be square to the wave face
- if they are above, size will be under estimated.
- if they are below, size will be over estimated.
2. Surfer's size and stance vary.
3. Difficult estimating with prone craft.
4. Becomes inaccurrate at larger wave sizes.

b. Wave size is calculated by comparison with the height of the rider by the rider.

Objections
1. Observer is in the least objective location, and possibly more focused on the factors of steepness and speed..
2. Surfer's size and stance vary.
3. Difficult estimating with prone craft.
4. Becomes extremely inaccurrate at larger wave sizes.

4. Scale?
a. Feet - Metres - Fathoms - Cubits?
The traditional surfing measurement scale has been Imperial (feet), for both waves and surfboards.
With metric standardisation in the scientific community, wave heights from meteorological sevices are in metres.
If the measurement is reasonably accurrate, the scale is unimportant - it can be readily converted to a familiar one.
For example : 1 metre = approximately 3.25 feet

b. Head-high
A measurement based on rider height, see Objections 3a. and 3b. above.


REFERENCES

Bascom, Willard : Waves and Beaches
Anchor Books
Doubleday and Company Inc.
Garden City, New York 1964.

Bascom, Willard : The Crest of the Wave - Adventures in Oceanography
Harper and Rowe Publishers, New York 1988

Dixon, Peter L. : Men and Waves : A Treasury of Surfing
Coward - McCann, Inc. New York 1966
Part II : The Science, Pages 71 to 90
Reprints text and diagrams from The Surf : Chapter VIII, Willard Bascom : Waves and Beaches, 1964

Dixon, Peter L. : The Complete Book of Surfing
Longmans, Green and Co Ltd., 40 Grosvenor Stret, W. 1. 1965
Chapter 4

Kahanamoku, Duke With Brennan, Joe:   Duke Kahanamoku’s World of Surfing
Angus and Robertson Publishers Sydney , Australia  1968
2nd Edition  A&R Paperbacks, Sydney , Australia 1972

Blake, Tom : Hawaiian Surfriders 1935
Mountain and Sea Publishing, Box 126 Redondo Beach California 90277 1983
Reprint of Hawaiian Surfboard, Paradise of the Pacific Press, Honolulu, Hawaii 1935

Kuhns, Grant : On Surfing
Charles E. Tuttle Company. Rutland, Vermont and Tokyo, Japan 1963
Chapter 7

Klein, H. Arthur :  Surfing
J.B.Lippincott Company, Philadelphia and New York 1965  Chapter H

Kelly, John  M:   Surf and Sea
A.S. Barnes and Co.Inc., 8 East  36 Street New York  16, New York  1965
Chapter 8.

Farrelly, Midget. As told to McGregor, Craig : This Surfing Life
Rigby Limited, James Place, Adelaide  1965.
Chapter 4

Cook, Joseph J. and Romeika, William J. :  Better Surfing
Kaye and Ward Ltd. 194-200 Bishopsgate, London, E.C.2 1968
Pages 20 - 23

Young, Nat ; Photographs by McCausland, Bill:   Nat Young’s Book of Surfing
A.H. & A.W. Reed Pty. Ltd.  53 Myroora Rd, Terry Hills, Sydney. 1979
Chapter 8

Abbott, Rick and Baker, Mike (Illustations)  Start Surfing
Stanely Paul and Co., 3 Fitzroy Square, London. W1P6JD 1980
Chapter 4

Orbelian, George : Essential Surfing
Orbelian Arts 100 Alto Avenue San Francisco CA 94116 1982
Pages 66 - 68

Atkins, Alan (ed)  : The Basics of Surfing
The Australian Surfriders Association Shop 8, Surf Coast Plaza, Torquay, Victoria, 3228, and
The Australian Council for Health Physical Education and Recreation Inc.
128 Glen Osmond Road, Parkside, South Australia 5063 1986.
Chapters 1.1 and 1.2

Lowdon, Brian J. and Lowdon, Margaret (eds.) :  Competitive Surfing - A Dedicated Approach
Mouvement Publications, Torquay, Victoria 3228, Australia  1988
Chapter 5, Peter Cole : Surfing Big Waves,  and  Chapter 14, Flynn, Stanford and Baker : Dynamics of Competitive Beaches

Finney, Ben and Houston, James D. :   Surfing – A History of the Ancient Hawaiian Sport
Pomegranate Books P.O. Box 6099 Rohnert Park, CA 94927 1996
Hawaiian Surfing Terms used in this article from Appendix A, pages 94 - 96

alt.surfing Dicussion Board : How do you measure wave size?
http://area51.upsu.plym.ac.uk/~ric/alt.surfing/wavesize.txt
An edited and annotated copy of this dicussion is included in the Appendix A, below.

Warshaw, Matt :  Mavericks  – The Story of Big Wave Surfing
Chronicle Books, Inc.  85 Second Street, San Francisco, California 94105 2000

Bryant, Edward :Tsumami - The Underrated Hazard
Cambridge University Press, The Pitt Building Trumpington Street, Cambridge, United Kingdom. 2001 Chapter 2.

Greg Small (Associated Press) : Isle converts to global  wave measures
Honolulu Star Bulletin Online EditionSunday, June 24, 2001
http://starbulletin.com/2001/06/24/news/story10.html



MY RESEARCH
1. After many years discussing wave size, I came to agree with John Kelly Jr. who proposed  two ways of measuring waves - you can over estimate or you can under estimate...

 John Kelly on Measuring Wave Heights
Of all the controversies that surround the surfing community, none burns brighter than the question, "How big are the waves?" Belligerents divide into two camps, the underestimators and the overestimators; few just plain estimators venture into the no man's land between. Pride, fear, subterfuge, unwarranted honesty, status seeking, rationalization, poor eyesight, revenge, negligent homicide and ignorance keep the fires of battle perennially stoked.
At the root of the difficulty are the awe of the inexperienced and the lack of reciprocal sympathy by the experienced. Add to this chronic condition, the differences in perspective between the beach-sitter who measures distant waves by the space between his thumb and forefinger, the rider who adds height and speed, and the unlucky gremlin, carried over the falls on his first try in big surf, who squares the distance from his eye level to the trough.
from Kelly :Surf and Sea, 1965. page 222.



2. Kelly supported his scepticism of scientic calculation by noting that the scientsts were not out in the surf....

John Kelly's Objection to Scientific  Wave Height Calculation
Oceanographers say the height of a wave is the vertical distance from its crest to the bottom of the trough. A fine academic definition, but how many oceanographers are seen out in the surf actually measuring waves? It's a touchy subject, even for scientists.
from Kelly : Surf and Sea, 1965. page 223.



3. I first encounted Willard Bascom's method  in his autobiography, The Crest of the Wave - Adventures in Oceanography.
I was not only impressed with the simplicity of the method, but his dynamic account of surf surveying circa 1945. These calculations were required  because the scientist was out in large surf, note Kelly's objection above.

Willard Bascom : Figure 57 : Surf Surveying , circa 1945

FIG. 57. Surveying in the surf.
Dukw is overtaken by a breaker as it moves landward along a course marked by range poles.
Man in Dukw heaves lead and calls "mark" into radio followed by measured depth.
Transit man on beach reads angle; an assistant seated by the radio receiver records both depth and distance.
from Bascom : Waves and Beaches, page 40.
Plate 1 : Dukw surfboarding on twelve foot plunging breaker during a beach survey (University of California).
from Bascom : Waves and Beaches, Plate 1 facing page 68.

4. I also noted that the method was originally devised in 1945, yet as far as I knew had never appeared in the mass of surfing literature produced since then.
I uploaded Bascom's method to surfresearch.com.au in May 2002.

Text uploaded to surfresearch.com.au  May 2002.
We learned a simple way for a person on the beach to measure the height of the big breakers, even though they are far offshore.
Just stand at a level on the beach where your eyes are exactly aligned with both the high point of the breaker and the distant horizon; then the height of the wave is the vertical distance between your eyes and the backrush.
We would often do that before risking a run through the surf, but rarely did we do it long enough to get the highest breakers, because wave heights vary so much.
We found that about every 3 minutes there would be a series of three higher-than-average waves.
But sometimes, because the three highest in one group were not the same height as those in the next group, we got into trouble. (My emphasis)
Bascom, Willard : The Crest of the Wave - Adventures in Oceanography
Harper and Rowe Publishers, New York 1988. Page 7


5. Because there was no accompanying diagram I prepared my own, also uploaded in May 2002.
Image uploaded to surfresearch.com.au  May 2002.
Very poor diagram by Geoff Cater, May 2002
This image supplemented, August 2002, see 10.below.
6.  I subsequently procured a copy of Willard Bascom's Waves and Beaches, the text and diagrams providing the foundation for this article. Concurrently (and coincdentally) I also accessed Peter Dixon's excellent anthology, Men and Waves : A Treasury of Surfing, 1966, that reprints Chapter VII : The Surf of  Willard Bascom"s  Waves and Beaches in Part II : The Science, Pages 71 to 90.
7. In July 2002, searching through google.com I found several  dicussion boards on the topic of measuring wave height, one of which http://area51.upsu.plym.ac.uk/~ric/alt.surfing/wavesize.txt contained a spiritited and informative discusion.

Some of these contributions are quoted in the notes above, an edited and annoted copy of the complete correspondence is included in  Appendix A.
One contributor offered Willard Bascom's method, but their posting was totally ignored by the following contributors.

alt.surfing Post #8 szborges@dale.ucdavis.edu (Will Borgeson)   Date: 22 May 1996
In case anyone is interested, here's Willy Bascom's technique for measuring wave height from shore:

"Simply stand on the beach at such a level that the tops of the breakers are exactly in line with your eye and the horizon. The vertical distance between your eye and the 'backrush curl' (upper edge of water on the beach) is equal to the height of the breaker."
Quoted from Bascom : Waves and Beaches, 1964.
The text in bold added by Will Borgeson to explain the difficult concept of "backrush curl".

So, if you're 6'tall and there's about 12' of height between the top of your head and thewater line, you're looking at 12' faces. This technique can be useful if there's no one out, the surf looks pretty big, but is way out there and hard to judge.

Will
NOTE : Apparently no-one was interested, this method was subsequently ignored by all further postings.



8. google.com also turned up an article featured at the Honolulu Star Bulletin Online Edition Sunday, June 24, 2001 by Greg Small
(Associated Press) entitled Isle converts to global  wave measures : Wave heights taken from the front go against the traditional method of measure that reports The wave reporting system changed in April , when the weather service finally convinced observers to report the full-face value of waves. The text of this article is included in Appendix B, below.

9. Initial research readily identified the discrepancy between measuring deep water waves and measuring breakers, however an understanding of breaking waves mechanics rquires further research. Bascom's Figure 15  illustrates some of the internal forces.

Willard Bascom : FIG. 15 Breaking wave forces

FIG. 15. The movement of a wave as it breaks in a wave channel (from motion picture analysis)
from Bascom : Waves and Beaches, page 40.
10.Supplementary Image, August 2002.

Goodvibes Surf Check circa 1973, after Bascom/Edwards.
Digital manipulation by surfresearch.com.au, 2002.
11. After copying and editing the alt.surfing dicussion and futher research, this page was uploaded to surfresearch.com.au in August 2002.


APPENDIX
Copyright Note : The pages below are reproduced here because of the lack of an archival tradition by online media and changes in location fail to guarantee future access. Anyone who wishes their contributions removed, please conact the editor.

Appendix A : Edited Postings from Newsgroups : alt.surfing
http://area51.upsu.plym.ac.uk/~ric/alt.surfing/wavesize.txt
Subject : How do you JUDGE WAVE SIZE?
Editing, highlighting in bold and additional text in italics, by Geoff Cater, July 2002.


Post #1  jona@aloha.net (jona )    Date: Sat, 11 May 1996
I hear lots of different methods of judging wave size.
I'm going to take a survey - check the one you believe is correct; one answer only.
(We all know what is supposed to be the correct way, right?)
Method
1. face of the wave just before it breaks
2. some portion of the face of the wave before it breaks
3. open ocean deep water swell size
4. back of the wave
Scale
consensus (I heard others say it was ___ feet)
conservative (in Hawaii this would be ____ feet)
local standards (in our locality it would be ___ feet)
double (or whatever) overhead

Post #2  mesa2@ix.netcom.com (Rick Ciaccio)   Date: 11 May 1996
Around here (?) the general consensus is:
4 foot swell reported meansoverhead surf;
6 foot swell means double overhead;
6 foot S (Simpson Scale?) Wedge swell means triple overhead+  :-)

We judge 'em from trough to lip with a surfer on it, we always refer towave size by face.
We always refer to Wedge wave size by "Simpson Scale" -
Fred (Simpson?)'s (of Viper Fins) own interpetation which has become the standard,
much like the illogical Hawiian way of calling them.
Generally, we reduce it to "good", "fun", "pounding", or "slamming",
that pretty much says go out.

When posting in alt.surfing I call them in face size from trough to lip
as they pitch (honest).
Rick



Post #3 Ric@diltd.demon.co.uk (Ric Harwood)   Date: Sun, 12 May 1996
Interesting question as there are surfers from all parts of the world here.

some portion of the face of the wave before it breaks
Top 2/3 as seen from the beach.
This eliminates the run out in front of the face as it is not steep enough to derive any power off,
but still looks like "height" from the front.
Ric
<irl://thereis.nothing.that.agood/days/surfing/can't/cure.exe>
PGP: 0766ABE5 | Homepage http://area51.upsu.plym.ac.uk/~ric/



Post #4  tbmaddux@alumnae.caltech.edu (Timothy B. Maddux)   Date: 14 May 1996
In direct comment on Post #3 ...
What about when you're surfing those gnarly suckout reefs
where the aforementioned "run out" is actually a steep
concaving below-sea-level nightmare?
Poses the question : To measure or not to measure the trough?
Tim Maddux -- tbmaddux@engineering.ucsb.edu
Santa Barbara Surfing -- http://www.engineering.ucsb.edu/~tbmaddux/

Post #5 Ric@diltd.demon.co.uk (Ric Harwood)  Date: Thu, 16 May 1996
Reply to Post #4...
I wouldn't know, [as I'm suffering from a sucking reef defiency {:^(  ] - humour

How would  you measure these?

Ric
<irl://thereis.nothing.that.agood/days/surfing/can't/cure.exe>
PGP: 0766ABE5 | Homepage http://area51.upsu.plym.ac.uk/~ric/



Post #6  OceanRider <oceanrider@prtcl.com>  Date: Sat, 18 May 1996
Humour...
Hey I've got a great idea!!!
All of you sit on the beach and figure out how big the waves are, while I go surfing!
My favorite surfer is the one sitting on the beach anyway!

Happy figuring, Glenn



Post #7  tbmaddux@alumnae.caltech.edu (Timothy B. Maddux)  Date: 19 May 1996
In reply to Post #5, the question about measuring the trough (a concaving below-sea-level nightmare), humorous...
1. From the beach at a safe distance away, or
2. by having a friend photograph me as I get pitched over the falls,
then using my outstretched 6' frame to accurately measure the wave heights.
3.The amount of my body sticking straight up out of the water upon impact
into the sand or reef could also be easily used to determine the depth of
water at breaking as well.

Tim Maddux -- tbmaddux@engineering.ucsb.edu
Santa Barbara Surfing -- http://www.engineering.ucsb.edu/~tbmaddux/



Post #8 szborges@dale.ucdavis.edu (Will Borgeson)   Date: 22 May 1996
In case anyone is interested, here's Willy Bascom's technique for measuring wave height from shore:

"Simply stand on the beach at such a level that the tops of the breakers are exactly in line with your eye and the horizon. The vertical distance between your eye and the 'backrush curl' (upper edge of water on the beach) is equal to the height of the breaker."
Quoted from Bascom : Waves and Beaches, 1964.
The bold added by Will Borgeson to explain the difficult concept of "backrush curl".

So, if you're 6'tall and there's about 12' of height between the top of your head and thewater line, you're looking at 12' faces. This technique can be useful if there's no one out, the surf looks pretty big, but is way out there and hard to judge.

Will
NOTE : Apparently no-one was interested, this method was subsequently ignored by all further postings.



Post #9  mundaka@acca.nmsu.edu (mundaka) Date: 13 May 1996
Double or whatever overhead. (Kinda hard to judge feet anyway.)
---No hay pedo!---

Post #10 "N. Briggs" <briggsn> Date: 16 May 1996 02:17:08 GMT
Seems to me that if you estimate the wave size in proper feet (the ones used on land) then half if, you're getting close.

Post #11 jritchie@iafrica.com Date: Tue, 14 May 1996 21:36:51 -0700
Here in Cape Town we also have these arguments.
Lank (?) of my friends judge from the front, but where I come from (Victoria Bay) it was judged at the back.
I'm so used to
6 feet being way overhead (
1 foot being knee-height,
2 feet being waist to chest height,
3 feet being chest to head height,
4 feet justover head height,
5 feet being overhead)
that when my friends tell me a size, it's completely different (usually smaller) than what I imagined...
Craig

Post #12  graham@big-g.win-uk.net (Graham Harrop) Date: Wed, 15 May 1996
I'd say(2) "some portion of the face of the wave before it breaks"
and like Ric (Post #3 ) and Craig (Post #11), it's about 2/3rds of the shoulder.
To me, a 4 foot wave is a 6' face. Set waves (say best of six), not the average.

Predicting waves is my job and I'm amazed at the lack of consensus on wave heights.
If we used Hawaiian scales here in the UK it'd be inches, not feet.
And then there's the French who use something called "metres".

As long as we're consistent, we'll understand each other.
Maybe it'd be better to say "shoulder-hopping", "head high", "overhead" or "double overhead". - The head-high scale
Good thread, Graham
Big G.
graham@big-g.win-uk.net



Post #13 Ric@diltd.demon.co.uk (Ric Harwood) Date: Thu, 16 May 1996
 20:27:07 GMT
In direct reply to Post #12, an objection to using a Head-high scale...
I'm liking this more and more.
But then I chat to my knee board friend and we have to convert in and out of feet again 'cos he keeps talking about these shoulder high "overhead" waves!
Ric
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Post #14 graham@big-g.win-uk.net (Graham Harrop) Date: Fri, 17 May 1996 12:19:38 GMT
Direct reponse to post #13...
Oooh, you bitch, Mail bomb on the way,
Graham.
Assumption : Graham is  'the knee board friend'  in Post #13

Post #15 Ric@diltd.demon.co.uk (Ric Harwood) Date: Tue, 21 May 1996
Direct reponse to post #14...
Not at all. *he's* the lucky one who hets to surf overheads all the time!
Ric
<irl://thereis.nothing.that.agood/days/surfing/can't/cure.exe>
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Post #15 salmonm@batis.bis.und.ac.za (MR Salmon) Date: 23 May 1996 08:53:03 GMT
Direct reponse to Post #12 and Post #13 on the Head-high scale...
Who really gives a shit?
The only people who you should be able to relate to are your friends
- as long as you say a 6 foot wave and they know hwat you're talking about, then you're fine.
Judging wave size is never gonna be consistent world-wide, so who cares?
MATT

From: njtravis@cse.lbl.gov (Nancy Jean Travis) Date: 23 May 1996
Reponse to Post #15 ...
Now I like calling them small.
If I say it was 3 foot, my friends understand it was pretty hot.
I remember a Billabong Pro at the Lane when Munga (Barry) took a barrell as big as the cliff and
the announcer called it 12.
F#$k, I thought, its 25 easy.
I remember it intimidated me horribly.
On another day at Sewers which I would have called 15 foot, Moth was screaming its a perfect 5!
I couldnt even get out the back that day.
Now I just cut the face in half and subtract a foot.
This really irks people who have an attachment to reality which is even more amusing.
So yeah, the day I surfed North Point in Cowaramup it was a lovely six feet, double overhead bombs. B-).
The wave I broke my board on was asolid 3 foot, hahaha.
fang

Post #17  the Sandman <whammer@whammer.com> Date: Thu, 23 May 1996
Direct reponse to Post #15 and Post #16
we've alot of kooks round here that have to plug the actual wave size in a function() ;-) to get the the wave size that they'll
tell you.
For the life of me I don't understand it.
I guess my life is complicated enough not to add another layer to it.
What I see is this; I'm surfing in double-0 conditions and they're on the beach debating wave height.
Kooks unite and hash out a standard.
When your done, paddle out and let me know...if ya can
the Sandman
http://www.whammer.com
Odds are, you're probably a kook

Post #18  leepadr@coastalnet.com (Lee Padrick)Date: 17 May 1996
Response to Post #11
I agree for the most part with your size descriptions.
I'm from North Carolina, stand 6' 3" tall and usually call a chest-high wave about 3 feet.
I usually amused by shorter guy (or girls) who call chest-high 5 feet (or larger).
But then again, if you get pitched by an 8-foot peak, you're gonna fall 8 feet!
Lee Padrick
<leepadr@coastalnet.com>

Post #19 Einstein <einstein@mars.superlink.net>Date: Wed, 22 May 1996
Resoponse to Post #18
Dude I am 5'10" and learned a three feet wave is over my head from the inside.
"Imagination is more important than knowledge!"
Einstein
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Post #20  JIMSLADE@msn.com (James )  Date: 20 May 96
Who cares? If it swells, ride it!
I've been listening to this shit for years and it doesn't matter how you measure a wave, its how you surf it!
If your not sure just look at it and make up a good lie like everyone else!


Post #21  robt2@ix.netcom.com(robert brannan ) Date: 20 May 1996 05:03:18 GMT
All wave size judgement is correct for your locale, it more reflects the consistency and size range for your area.
We measure reams of cloth in yards, height of men in feet, cigarette length in millimeters.
However for waves, we all use feet, but each geographic locale has a different consistency and size range,
-- thus we change or stretchor shorten our rulers.
It gives us all a better feel for the variability of size that exitsts at our own breaks.
I've seen some winter's so consistent with new 4-6'swells every 3-4 days and bigger, that when I pass a friend and ask for a report and viceaversa, we would just reply
" It was good, it will be good tomorrow" or "It was good, it will be smaller tomorrow"

Post #22 gjohnson@dream.season.com (Reality is a point of view) Date: 20 May 1996
Reponse to Post #21
I've heard a similar suggestion for call/fax/net surf reports.
Gary Johnson "There's no union called the AFL-CIA is there?"
gjohnson@season.com <a href="http://www.efm.org">Walk The Talk</a>
CAMPAIGN '96: Juck 'em if they can't fake a toke.

Post #23 sponge@news.ohana.com (Neal Miyake) Date: 15 May 1996
In Hawaii, we "measure from the back," meaning, we essentially cut the wave face height in half.
The reason (I think) is because of Californians in the 50s and 60s sandbagging to surprise newcomers to the islands.
I know it's stupid, but it's the standard that everyone uses.
Nowadays, if you don't call it like the locals do, you'll be put down bigtime.
The local media, especially the radio, perpetuate the underestimating.
So, three feet is head high, six is double overhead.
Don't even ask what twenty-five is.
When I was working at the Eddie in 89, I asked the judging panel how big they thought it was.
There was a long silence before someone (I thinkJack Shipley) said, "Overhead!"
I guess only Ken Bradshaw is allowed to make the call at Waimea.
Interesting personal observation: a six foot wave in the Country is bigger than a six foot wave in Town.
sponge
P.S. Right now, Town is one-to-two feet.

Post #24 surffohio@aol.com (SurffOhio) Date: 15 May 1996
Response to Post #23
Apparently the reason is due to scientific fact. See below.
Today my daughter got her Exploring The Ocean book from World Book.
They had a chapter called Wave Makers. The following is an excerpt.

"The height of a wave is measured from its crest to its trough.
The crest is the wave's highest part or peak.
The trough is the lowest part, the depression the wave makes in the water's surface."
This is the correcct method of measuring deep water waves only - and is not applicable to breakers.
The picture illustrated the trough as being the depression between two waves, not the face before it closes out on the beach.
So, with the above data the Hawaiians and World Book are in full agreement.
I am glad. I don't want to see my 10 year old get confused. :-)
This does bring up a question.
If one is riding 25 ft Waimea is he dropping down a 50 to 75 foot face?
Or, is the face height used since it would sound much more significant than a 10 to 12 footer?
If I dropped down a 25 ft face at Waimea, I would at least feel like I had ridden a 25 ft wave
(after I had gotten done peeing all over myself).

Sorry Rick C., I guess you've been getting pounded by 3 footers at thWedge all this time. :-)
I want my damn money back for all those pics yousold me of the Wedge!!!!
Ok...........just kiddin.
Surff



Post #25 Ric@diltd.demon.co.uk (Ric Harwood) Date: Thu, 16 May 1996
Response to Post #23 and #24
Sure. If this were sci.geo.ceanography the waves are described by these characteristics:
L= Wavelength, [peak to peak, trough to trough...]
C= speed, [don't let's get started on that one.]
T= period, [time for one L to pass a point, or time between zero upcrossing periods.]
H=Height [Vertical height between bottom of trough and top of peak.]
Again, this is the correcct method of measuring deep water waves only - and is not applicable to breakers.
a= Amplitude [Displacement from Mean Sea Level, (H/2) ]
Steepness  = [ H/L ]
k= wave number [ 2pi/L]
and a few other more obscure ones.

When you look at the face of a wave from the beach you see H.
However you will usually see a surfer playing on just the top 2/3 of this H because the bottom 1/3 tends to not be steep enough to surf, even on a steep wave. (Common, but not always correct)
Perhaps this is rather different on very abrupt reef edge breaks.

I'd be interested to see a description from those with more experience of these than I do.
[that must include a lot of you,because I don't have any yet... {:^( ]
ATB
Ric
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Post #26 mesa2@ix.netcom.com(Rick Ciaccio) Date: 17 May 1996
Doesn't every clique or group have their unwritten or unspoken way of communicating?
We use words like "pound" and "slam", or at the other end of the scale "queenie".
When you include the word "pound" in your sentence why do you need to measure it?
Rick

Post #27  tbmaddux@alumnae.caltech.edu (Timothy B. Maddux) Date: 17 May 1996
Reponse to Post #24, Measuring deep water waves = The Hawaiian method...
[ rant mode on ]
Actually, they are not in agreement.
Wave height as the World Book defines it it is precisely the distance from the top of the crest to the bottom of the trough.
So, a breaking wave's height would be the distance from the top of the crest to the bottom of the trough,
at the exact moment when the wave *just* begins to break, or when the water particle velocity at the crest is equal to the wave's phase speed , and the lip just starts throwing out.

To put it another way, the "height" of a wave is always defined in the same manner, be it a breaking wave, shallow water wave, or deep water wave.(not necessarily correct, shallow water waves of tanslation do not have a trough.)

If you had a wavewire out in a Hawaiian break, under monochromatic wave conditions (all the same height and period), the wire would record exactly the same difference in water surface elevation from the crest of the wave to the trough in front as it breaks as the difference from that breaking elevation to the trough after it passes by, i.e. the backside.

The only way to get away with describing a measurement as "from the back" and actually MAKING such a measurement is by doing so on a very shallow water reef surrounded by open-ocean depth water.
Each wave crest could approach and shoal and break while the following trough and crest behind it were still at their deep water values and essentially negligible.
Then the distance from trough behind to breaking crest would approximately be half that of the breaking wave in front.

Hawaiian reefs, however, shoal up more gradually than this, as evidenced by many photos in the mags of lines of black walls to the horizon.

[ rant mode off ]

They're not measuring from the back, they're just dividing the actual breaking height by 2.
Quoted from Post #24 :
"This does bring up a question. If one is riding 25 ft Waimea is he dropping down a 50 to 75 foot face?"
Answer : Roughly 50 feet, yes.
Tim Maddux -- tbmaddux@engineering.ucsb.edu
Santa Barbara Surfing -- http://www.engineering.ucsb.edu/~tbmaddux/



Post #28 dfrick@lava.net (Doug Frick) Date: Fri, 17 May 1996
Reponse to Post #27, Quotes and answers...
Quote from Post #24 :
"Hawaiian reefs, however, shoal up more gradually than this, as evidenced by many photos in the mags of lines of black walls to the horizon."
Answer :
Another possibility is that those black walls are essentially open-ocean waves.
Quote from Post #24 :
"They're not measuring from the back, they're just dividing the actual breaking height by 2."
Answer :
Well, theory aside, I do measure from the back.
When I see a surfer kick out and the backside that he's coming down on is twice his height, that's about a twelve foot wave.
If you watch the next set come in from the front, the wave is probably four times the surfer's height from top to his bottom turn;
that's twenty-some feet.
After a few years of guessing wave heights and getting agreement (or ridicule) from the bruddahs, you know what the local standards are. (They do vary on different parts of Oahu.)
I'm not disputing your definition of  (deep water) wave height (at least it's consistent) or the behavior of monochromatic waves. Theory's good for wave tanks.
Quote from Post #24 :
"This does bring up a question. If one is riding 25 ft Waimea is he dropping down a 50 to 75 foot face?
Roughly 50 feet, yes."
Answer :
Agreed.
Doug Frick
dfrick@hcc.hawaii.edu
dfrick@lava.net

Post #29 Ric@diltd.demon.co.uk (Ric Harwood) Date: Sun, 19 May 1996
Response to post #28
In alt.surfing, dfrick@lava.net (Doug Frick), Doug Frick wrote:
Quote from Post #28 : "Another possibility is that those black walls are essentially open-ocean waves."

Not really AFAIK, the ocean swell waves [deep water, depth>(L/2) will have a height of a couple of meters or so and a length of the order of a couple of hundred meters.

Wave looking steep and dark are generaly feeling the bottom.
Ric
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Post #30 tbmaddux@alumnae.caltech.edu (Timothy B. Maddux) Date: 19 May 1996
Another response to post #28
Quote from Post #28
"Another possibility is that those black walls are essentially open-ocean waves."
Reponse :
Open-ocean waves are exemplified by incredibly low steepness... a 10 ft. 20 s. wave has an open-ocean wavelength of gT/2pi = 31 m, which means the 3 m of height difference is spread out over 15 m, not much of a wall.
Quote from Post #28
"Well, theory aside, I do measure from the back. When I see a surfer kick out and the backside that he's coming down on is twice his height, that's about a twelve foot wave."
Reponse :
Ah, but you're not waiting long enough... if you wait for him to get ALL the way down the back, which would be in the trough of the approaching wave as it begins to throw, then the backside and front side would appear about the same.
Once a wave starts to break, its carried energy starts to dissipate, which is seen in a reduction of the wave's height.
So if you watch the backside of the wave as he floats down it, you'll notice that it's decreasing as it moves shoreward.
Quote from Post #28
After a few years of guessing wave heights and getting agreement (or ridicule) from the bruddahs, you know what the local standards are. (They do vary on different parts of Oahu.)
Reponse :
As my surf reports show, I just use face-of-wave estimates based on human proportions (v.s. a 6' tall person). It's my understanding that this is still o.k. in the Islands, i.e. a 3' Hawaiian wave or 6' Cali wave are both about head-high... right?
Tim Maddux -- tbmaddux@engineering.ucsb.edu
Santa Barbara Surfing -- http://www.engineering.ucsb.edu/~tbmaddux/

Post #31 carley@manly.civeng.unsw.edu.au (James Carley) Date: Mon, 20 May 1996
Response to Post #30
Quote from Post #30
"Open-ocean waves are exemplified by incredibly low steepness... a 10 ft. 20 s. wave has an open-ocean wavelength of gT/2pi = 31 m, which means the 3 m of height difference is spread out over 15 m, not much of a wall."
Response :
Sorry to be a smartarse Tim but your theory is a bit wrong.
Deepwater wavelength should be

L= gT^2/2pi

or L = 1.56 T^2 where T is wave period

which for your 20 s period wave gives L = 624 m
or more realistically T = 15 s gives L = 351 m
 

Someone else wrote: (Quote from Post #28)
"After a few years of guessing wave heights and getting agreement (or ridicule) from the bruddahs, you know what the local standards are. (They do vary on different parts of Oahu.)"
Response :
This describes the macho height system well, it's all about peer group acceptance rather than science.
Do they call their 9' board a 4'6"?

I'm another who measures waves scientifically as part of my job.
In real terms this means that a head high breaking wave is ~6 feet.
When discussing with pseudo machos I use the HEAD scale or sometimes to confound them (and in my own reference scale)
I say an X metre face 'cause metric is the future.

James Carley
Water Research Laboratory
University of New South Wales
Sydney, Australia

James Carley
Sydney, Australia
carley@manly.civeng.unsw.edu.au



Post #31 dfrick@lava.net (Doug Frick) Date: Mon, 20 May 1996
Reponse to Post #30
The topic of this thread is "How do you JUDGE WAVE SIZE?"
You judge it scientifically. That's nice.
But if you come to Hawaii and say you ride fifty-foot waves, nobody is going to believe you.
Thescientific measure you're using is nothing more than a method accepted by your 'science' peer group.
I'm not saying there isn't astandard scientific measure, it just isn't the one used where I surf.
(And I made that disclaimer in my post.)

My 9'6" is 9'6", as agreed upon by my peer group of measuring tape owners.

Doug Frick
dfrick@hcc.hawaii.edu
dfrick@lava.net



Post #32  tbmaddux@alumnae.caltech.edu (Timothy B. Maddux) Date: 24 May 1996
Response to post #31
Would they believe me if I called a double-overhead wave as 6 feet, assuming everyone accepts that the wave really is double-overhead on the face?

Most people in the area where I surf use "faces" and "backs" to make the distinction between full-sizing and half-sizing
the wave heights. There's usually very wide scatter in the assessment of wave heights, most easily judged from land and
most adrenaline-elevated when ducking them.

I have my own bias when making reports, I won't typically report the larger heights of set waves unless I either surf
a few myself or get pounded by them in a noteworthy fashion.
Otherwise it just doesn't count.
Tim Maddux -- tbmaddux@engineering.ucsb.edu
Santa Barbara Surfing -- http://www.engineering.ucsb.edu/~tbmaddux/



Post #33 dfrick@lava.net (Doug Frick) Date: Mon, 20 May 1996
Response to Post #30
Quote from Post #30
"Open-ocean waves are exemplified by incredibly low steepness... a 10 ft. 20 s. wave has an open-ocean wavelength of gT/2pi = 31 m, which means the 3 m of height difference is spread out over 15 m, not much of a wall."
Response
Yeah, I saw I was wrong on that one after I went and looked in my ocean textbooks.
On big north swell days at Makaha, you can watch the sets going by on the horizon, perpendicular to shore (Makaha faces west), as well as watching the (wrapped) sets coming straight in.
Quote from Post #28, re-quoted in Post #30
"Well, theory aside, I do measure from the back. When I see a surfer kick out and the backside that he's coming down on is twice his height, that's about a twelve foot wave."
Quoted response from Post #30
Ah, but you're not waiting long enough... if you wait for him to get ALL the way down the back, which would be in the trough of the approaching wave as it begins to throw, then the backside and front side would appea about the same.
Response
Yes, that is true. I'm not waiting twenty or so seconds to make my guesstimate (and believe me, I'll be about ten feet under the water when that next wave pitches). But that's my point. I'm not attempting to duplicate the scientific measure here. The method I use yields an answer consistent with the local description of wave size, which is what I'm trying to achieve.
Quoted from Post #30
As my surf reports show, I just use face-of-wave estimates based on human proportions (v.s. a 6' tall person). It's my understanding that this is still o.k. in the Islands, i.e. a 3' Hawaiian wave or 6' Cali wave are both about head-high... right?
Response
That's usually correct, and if you say "head-high" (as opposed to 6')people will know what you mean.

I'll stick my neck out here, and call a wave.
I have a picture of me out bodysurfing: http://www.lava.net/~dfrick/mz-1.jpg .
Slapping a ruler up on my monitor yields a face height of about 4 inches.
From my head to my outstretched hand is about 1/2 inch = 3 feet.
So I'd guess the face height is about 24' (do people actually say "quadruple overhead"?).
From my memory, I'd call this wave about a 10-footer, on a 12'+ day.

What matters most is that people know what the other person means, whether backs, faces, heads, or scientific.
When I quote Hawaii waves, I usually put (backs) after the height.
When I go to the Washington coast, I switch to quoting face sizes.
When I look in the databases, I expect scientific measure.
They all have their place.
Doug Frick
dfrick@hcc.hawaii.edu
dfrick@lava.net



Post #34: ric@diltd.demon.co.uk (Ric Harwood) Date: Wed, 22 May 1996
Response to Post # 33
Quote from Post #33
"What matters most is that people know what the other person means, whether backs, faces, heads, or scientific.
When I quote Hawaii waves, I usually put (backs) after the height.
When I go to the Washington coast, I switch to quoting face sizes.
When I look in the databases, I expect scientific measure. They all have their place."
Response
That's exactly it IMHO.
I the scientific context we would use meters, peak to trough, but at the beach that is meaningless in that everyone else there is using different 'scale', and each area has it's own scale. [almost but notquite entirely unlike feet].
Which is why jona started the thread in the first place.

The interesting/confusing thing here in alt.surfing is that there are people reading and posting from all these different places, so
it takes is hard to get the hang of what everyone means by "x foot", especially as many of us have not yet had the opportunity of surfing the world and knowing the length of the local ruler.

[Indeed the pleasure of a.s is being in touch with people who areout getting stoked all over the world]

Certainly the body sized ruler seems to the thing to use.
We all know how big out local "feet" are, and most of us will be within a couple of 'heads' of 6' tall.

Good thread Jona, thanks.
Ric
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Post #35 tdstearns@aol.com (TDStearns) Date: 18 May 1996
its pretty clear that feet and meters arent too great...changes from spot to spot and even wave to wave make "actual" size difficult to discuss..even if you count the back or the front.. youre going to get waves that come from a similar swell size and look totally different as theyre breaking...

maybe..as an earlier post said..the best way for surfers to deal with this (as opposed to the method from sci.geo.oceanography)..is just knee high..butt high...waist high..nipple high..etc..a 4 foot wave here is different from a 4 foot wave there..but if i say head high..you know about what im talking about...

i gave up using numbers......although i have few short friends who get a
little confused sometimes..."head-high?"

Toby - Oregon
No surf here, try WA



Post #35 dagum@barrel.asd.sgi.com (Leo Dagum) Date: 20 May 1996
It's all relative right?
If I'm out with a buddy and the waves are of any consequence, then we down play them.
Nothing is ever more than 'solid overhead' (even if they're 15' faces).
Or if one of them comes through a little mushy then we'll say "they're shouldering up a bit today", even though you just saw two perfect A-frames go by.
Maybe it's machismo but personally I think it's just an effective way of dealing with fear.
I'd rather delude myself by playing these games than admit the waves really are big and scary and end up paddling in (or worse yet, freezing up at the wrong moment and getting axed by one of those that didn't "shoulder up").
Of course if your buddies aren't around, then it's always "double overhead and hollow, you really MISSED it dude!"
But it's just games we play because if we really want to describe the surf we'll just rattle off the buoy readings for backup "10'/14sec from 285...SOLID overhead".
- leo
Leo Dagum
Supercomputer Applications Tel: 415-933-2179
Silicon Graphics, Inc. Fax: 415-933-3562
Mountain View, CA 94043 email: dagum@sgi.com
Post #36 surffohio@aol.com (SurffOhio) Date: 20 May 1996

Reponse to Post #27
Quote from Post 27
"So, with the above data the Hawaiians and World Book are in full agreement.
[ rant mode on ]
Actually, they are not in agreement. Wave height as the World Book defines it it is precisely the distance from the top of the crest to the bottom of the trough. So, a breaking wave's height would be the distance from the top of the crest to the bottom of the trough, at the exact moment when the wave *just* begins to break, or when the water particle velocity at the crest is equal to the wave's phase speed , and the lip just starts throwing out."
Response
....snipped the rest because I dont understand it and I started to feel dumb....
Jee whiz, my daughter and I just liked the cute picture in World Book about waves. :-)
Surff

Post #37  Einstein <einstein@mars.superlink.net> Date: Wed, 22 May 1996
I think the thickness of a wave plays an equally big part.
Like a wave of the same height in Hawaii is much better than the same sized one in NJ most of the time.
Its much more powerful and hollow!
Extended Quotes from Post #23 and Post #24
"Imagination is more important than knowledge!"
Einstein
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Post #38 Sgulie@ix.netcom.com (Steven Gulie) Date: Fri, 17 May 1996
Interestingly, the bouys that measure wave height, in ft or meters, don't bob up and down the height of the wave (they don't look over the edge and get scared, either).
They estimate the wave size by the angular momentum imparted when the wave passes under the tethered bouy.
This is a little like judging the size of a wave by how hard it rings your bell when it slaps you upside the head...
So that's how I measure it. Ow! Big one!

When I'm watching from the cliffs, I estimate wave height by the face *with a rider on the wave*.
If he's cruising down the line, and the lip is above his head, it's *overhead*.
This discounts the trough, since the rider is on the face.
If it's a sponger (prone rider), you can still guage it pretty well, since he's stretched out full length on the wave, and you can see
how high it is relative to a person's length.

A hollow wave is bigger than a crumbling wave of equal height. Huh? No, I mean it.
A wave pitches out because the bottom has gotten shallow so suddenly that it can't reach its full height.
A given reef can only take a wave of a certain size.
Any bigger and it either breaks on a deeper reef outside, or it buckles in the middle before it can even pitch out (weird
looking, when it happens).

Bizarre side waves like the Wedge defy this logic.
So much energy is running sideways and backwards up the beach that it's more like a waterspout than a wave in the classic physics model:
it does whatever the hell it wants to, including lurching 25' into the air when it's only 2'deep.

A question for da macho boyz who measure it "from the back": You saw it from the back? Why didn't you go?

Steve Gulie (sgulie@ix.netcom.com)
\... Wilbur would go...



Post # 39 Einstein <einstein@mars.superlink.net> Date: Wed, 22 May 1996
"Imagination is more important than knowledge!"
Einstein
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Post #40  jona@aloha.net (jona) Date: Tue, 28 May 1996
Conclusion by the author of Post #1
Thanks for the many replies this thread has elicited - lot's of good responses.
First, the answer: surf height is measured on the wave's face, from the trough to the crest.
Yes, I know that's just a textbook definition.

First point, the BIG GUNS.

I spoke with George Downing, one of the first inductees into Surfing's Hall of Fame here in Hawaii.
He makes the call on when to hold the Eddie Aikau Quicksilver Waimea big wave contest, minimum 20 ft
required for this contest.
George said, if you're talking about height use the "dictionary's definition" of height, "vertical", i.e.
vertical height of the face before it breaks, despite the fact that there is some addition of height because a wave sucks out some of the water in the trough.

I also spoke with Rick Grigg, oceanographer and long time big wavsurfer.
His answer was measure by the book (oceanography) - the height of the face, trough to crest.
He also brought up the interesting point of the psychology of judging wave height.
The "correct" measurement will assure acceptance/approval among other surfers (you're "in"); someone who doesn't know how to measure correctly is "out".
The idea of group identification is in itself another very interesting topic (new thread? maybe too much analysis; we surf because it's fun).

Another surfing great disagreed, however. Rabbit Kekai told me the height is measured from the back of the wave.

Second, artificial DISTORTION of what's plain.

Mark Cunningham, lifeguard at Ehukai Beach Park (Pipeline) admitted that surfers may have gotten jaded due to their familiarity with waves of all sizes.
This was in response to my claim that presently wave heights are underestimated compared to what we judged waves to be
around 20 years ago.
I lived and surfed on the North Shore of Oahu back then and it seemed people had some consensus about judging size.
(I still surf now too)

Another well-known big (or small) wave surfer, James Jones, said big waves are underestimated.
He said when it reaches 20 ft or more "all objectivity goes out the window".

George Mason, meteorologist and professional surf forecaster for Wave Track/Surfline said it's "like beating your head against the wall" in describing his efforts to persuade people that the correct measurement is the face of the wave.
In fact, the surf forecast from Wave Track/Surfline will mention "head high", etc. to escape the problem of varying scales of wave measurement.
Through George's efforts one of the daily newspapers prints the definition, height measured from trough to crest, under the daily surf forecast.

CONCLUSION - are we CONFUSED?

I have to admit that there is a good number of surfers here in Hawaii who believe the back of the wave is the height of the surf. The big problem with this is that is the back of the wave has a very gradual slope which makes estimating height very difficult, plus you can't see it from the land.

Anyway, replies to my thread reflect this confusion: changing judgement when in another locality, peer group scale, using a
body-size scale, reducing the face size by a factor. I contend the back of the wave measurement is also a reflection of a
too-conservative measurement.

Not only are surfers misled, the surf forecasters are influenced.
I am a meteorologist/forecaster for the National Weather Service in Honolulu (a neat job for which I thank the Lord).
I spoke against the back-of-the-wave measurement misconception with some of the forecasters here.
Even though they know what the book says - they were told by some of the surfers and county water safety employees
that surf measurement was actually the back of the wave!
We get surf observations from lifeguards and observers that seem to me to be on the conservative side.
(Peter Cole never has adjusted his scale downward though.)
You've heard of the difference in measuring north shore waves in Hawaii even compared to south shore waves.
So we as forecasters are caught in this cycle of incorrect measurements, yet we're issuing forecasts and even high surf advisories based on these "measurements".
I do still want to thank all water safety personnel who do a great and courageous job.
Inches of rain or snow are easier to measure, right?

MY PLEA

Let's quit worrying about what others think and call it like it is.
I know there is going to be some differences, but we could all realize the benefits of more uniform measurements between different locations around the world. (Sorry so long-winded, yeah!)

Jonathan Hoag



Appendix B : Greg Small (Associated Press)  in Honolulu Star Bulletin Online Edition
Sunday, June 24, 2001
http://starbulletin.com/2001/06/24/news/story10.html
Isle converts to global  wave measures
Wave heights taken from the front go against the traditional method of measure

You'd think that when it comes to surfers bragging about their prowess, the bigger the waves the better.

But not here in Hawaii, where one out of every 10 people surf and, in a sort of reverse-machismo, surfers traditionally report wave sizes smaller than elsewhere.

While the rest of the world rides five-footers, those same size waves in Hawaii would be dismissed as three-footers.

"They'd say 10 feet Hawaii size, which means 15 feet if you're from New Jersey," said Randy Rarick, executive director of Hawaii's Triple Crown of Surfing and regional director of the Association of Surfing Professionals.

"You're downplaying it to downplay the seriousness of it," said Rarick, who's also association vice president.

But wave size is taken seriously by the National Weather Service, which had to contend with wave height observations reported by island surfers and lifeguards that consistently fell short of forecast predictions.

The problem: Scientists and surfers were using different methods to measure the height of waves.

The weather service forecasts are based on the international standard of full-face value, measured from the trough in front of the wave to the top of the wave crest, said Robert Kelly, weather service director of operations in Hawaii.

But when Hawaiian surfers look at a wave across the water, they calculate from median sea level to the crest.
"Hawaii had a uniquely local system," Kelly said.

An estimated 120,000 islanders engage in surfing and similar activities, such as bodyboarding. The surfing association in Hawaii has 150 active members at the pro level and 1,200 members at the amateur level.

The wave reporting system changed in April, when the weather service finally convinced observers to report the full-face value of waves, but surfers aren't entirely giving up their laid-back assessment.

Surf forecasts issued by the weather service were reworded to take the change into account: "Forecast surf heights are estimates of the height of the face or front of waves. This may be up to twice the surf heights traditionally reported in Hawaii."

Will the change mar the macho image of Hawaii's sun-drenched surfers?
"Most surfers shrug it off and go, 'Whatever,"' Rarick said. "As a long-time North Shore surfer and resident, I have to scoff a little bit."

Oahu's North Shore, home of the famed Banzai Pipeline and Sunset Beach, is where the best surfers from around the world gather each year for the three surf meets that comprise the Triple Crown.

Rarick said Triple Crown officials will go along with the change, but won't completely abandon local tradition. Competitors will be told, for example, that waves will be 8 to 12 feet high with a 15- to 18-foot face, he said.

One surfer, who asked not to be identified, lamented the change officialdom has imposed on Hawaii's laid-back surfing community.

"The culture has been assaulted," said the surfer, who's been riding Hawaii's waves since the 1960s. "It's been an adjustment for the surfers, and they're laughing."

Ralph Goto, Oahu's Ocean Safety Division administrator, stressed that estimating the height of incoming waves isn't an exact science, because a lot depends on whether the observer is in a lifeguard tower, on the beach or in the water.

"No matter how you call it, it's subjective," Goto said.

© 2001 Honolulu Star-Bulletin http://starbulletin.com

Editor's note : Despite the well written and researched article, the Honolulu Star Bulletin loses credibility points by including a surfing photograph captioned A surfer sailed through one of the big waves at Sunset Beach in 1998.
The photograph is a large lefthand tube at Pipeline, surfer unidentified..


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