btw i hope the american fellows arent mistaking miles for kilometers
60 km/ph is 35 miles perhour
Hi Silly,
Thanks for your input mate, actually GPS units measure in 3 dimensions, so they do measure the speed of the drop as well, and that makes them pretty good for measuring surfing speed. Apparently MTB and Bill Barnfield, who have been using impeller based speedos along with GPS, have found that the readings agree closely (just what I read from one of Blakestah’s posts) which makes sense because GPs measures the vertical component as well.
Looking at the footage of James and his friends at the wedge the fastest part of the wave appeared to be the drop. . . and the GPS measures that which is probably why they managed to get 31mph.
75 metres over 3.5 seconds is about right ( easy peasy) for a sustained speed run, those boards have ‘long legs’ and cover the distance deceptively fast. . (just like the fat guys in the spy novels who move with surprising speed 
)
Cheers,
Roy
The best months on the East coast will be February through to July that way we catch the Cyclone season which can last until May, plus the midwinter swells, the East Coast goes through long cycles, like we had a couple of excellent years 2000 to 2002, it just seemed to pump constantly, the last couple of years have been poor, the El Nino again, but of course we still get some waves. On a good cycle we get constant Summer North swell from stationary tropical high pressure systems, plus cyclones added in to the mix.
A good idea would be to stay mobile so that we can hit the West coast and the South East coast as well. . . . maybe we could visit Silly’s neck of the woods if there are some good camping spots, just a few thoughts anyway.
Cheers,
Roy
well if a speedbump/shark bikky/eskylid can go 31 mph
i dont see why everyones having such a hard time believing you can get a board up to 35mph
were only talking 4 mph
wots the problem
and why the lock down
yeah sure
i know a few spots along the coast
id kinda rather keep it to ourselves though 
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…… i do have to question the accuracy of gps readings to measure speed on a wave though
…… i think you should consider a log device
and then all arguments would be moot
As long as you don’t block the signal from the satellite to the GPS receiver, and the speeds are measured by Doppler shift (rather than computed from distance per unit elapsed time measurements), the GPS measurements are: (1) quite accurate (probably more so at the kind of speeds and conditions that we’re talking about) than a log would be, and (2) as has frequently already been stated before, three-dimensional.
All arguments would not be moot using a log. Comparing the readings from a log device with the readings from a GPS device is like comparing apples with oranges. Again…log devices measure speed through the water, a GPS device measures speed relative to the earth. It is easily possible to have a speed through the water near zero (and measured by the log) at the same time that the speed relative to the earth (measured by the GPS) is greater than the speed of of the wave progression toward shore. For example, consider the late stage of a floater–the motion of the water past board is small since the two are nearly moving together; but relative to the earth the surfboard is going at least the rate of progression of the wave plus the vector addition of the downward speed of the “free-falling” board and surfer).
mtb
cheers for the info
Tom/Roy ,
the problem i have is the footage you posted in the past claiming outragous speeds that appeared to be going pretty slowly.once you have cried wolf 
no one believes you anymore
you always seem to be claiming one better
if i posted 40 i wouldent be supprised if you say you have hit 44 etc
my speeds were independently verified by 2 different people who both have the ride backed up on video.
to be honest i feel anything over 15 mph is starting to move and 18 to 20 is blazing fast
personally(off top of my head) i havent hit much over 23-24 mph on my air mat but i do not record every single session
wedge is a very special wave with alot of potential for speed the drop is some of it but that is not where the real speed comes . on the 31 mph wave the rider said he was going fastest at exit.
the speed comes from the 2 swells zippering together.
i claim the concept because no one used one for surfing before me. not even sure if the wind surfers had me beat .
have been useing the set up for at least 5 years before the geko even came out i had a bigger unit in a larger aquapak
please post a few videos of something other then the weak beachbreak i always see you on i would love to see you going
at the speeds you claim
I do not feel this thread should be locked but i am definetly in a put up or shut up mode with this discussion
Soul
if your talking about the wedge booger shots
they look slow!
i question your readings as those riders are hardly producing any wake
my gramma goes faster in her wheel chair
its amazing a surfcraft could appear to go so slow on such a powerful waves
maybe you got your geko wet
To put it bluntly, you are calling me a liar.
I have said it before and I will say it again: I have regular GPs readings above 30 mph including several above 35mph and one at 37 mph, the GPS is functioning correctly and it is being reported correctly.
Generally I have at least 3 witnesses to the speed recording event. . . . the fact that some of them are my family is irrelevant, they are honest people, say otherwise and you make yourself an enemy.
Although the whole purpose of using gps is so that we don’t have to rely on eyeballing video footage and making knee jerk judgements based on wave quality or board size, I have seen your video, it seems about right, top speeds between 18 and 31 mph. . . . . and your lids appear to me to be going a tad slower than my best speeds. … . but that’s just an opinion, the gps readings are the real test, and they show that you are slower.
I suggest that you chill out and stop making poorly veiled insults, how about you report what you have done and I will report what I have done, and let people make of it what they will? It spoils it to bicker and insults people’s integrity, so cut it out please.
My last comment is this: You say that 20 is blazing fast. … . . I find 20 to be rather slow, like 1st gear. … . 37 miles per hour is just the start, we will be doing over 40 very soon, just waiting for a cyclone.
Regards,
Roy
Hold up, Tom/Roy.
You said in a post above that for a minute long ride, you only take the fastest second. This in and of itself makes your determination of speed absolutely flawed and invalid. Of the 60 (or more) data points you gather, you only choose to report one?
How do you think pharmaceutical companies would feel if they only had to report the best case scenarios in clinical trials? They would be in heaven, and every drug on the market would grant eternal life in their advertisements.
Now, what about the rest of the readings for the ride? Give us a histogram of the readings throughout the fastest section of a ride (or even better, the whole ride), and we can then see what types of speed you are getting at. By reporting the outermost outlier point, you immediately invalidate your analysis of speed. I would be tempted to more readily believe the average of the top quartile of readings (maybe even 90th percentile), but not an outlier point.
To only include one point of data out of many is asking an awful lot of a GPS system in terms of accuracy.
Basically, statistically speaking, you have no ground to stand on as far as speed readings are concerned if you are going to sort through the data and present it as you do.
JSS
I tend to agree, a histogram or even an average speed would be the best measure.
Maxmercy,
i agree the full readings would be great if the wave was roughly the same speed for multiple seconds i do record the track and analize it
I have used the same program that the windsurfers use to analize the gps track but that is not something that is fully worked out its more of a back up to the reading using the dopler effect.
dopler is extremely accurate debatebly as long as the signal is not interupted which in theory is very possible in a tube.
under real life conditions i have been told that the gps will project your acceleration during periods where the signal was lost .
personally i used the gps for a while and noted the various readings as i rode after each ride
after a while you get a feel for it.you can call out the speed you were going within a mile or 2 before you look at the reading after a bit of time useing it.every once in a while you get an errant reading that seems a bit high or low compared to what you thought it would be. peak speed is a very valid thing to report but high readings need to be taken with a grain of salt. the more readings you can get on similar speed waves helps build a feel for it
I really wont go so far as to say Ron actually went 31 mph on that wedge wave ill say thats what the gps reported
here is the ride on video and the rider with 20+ years at the break in senior wave catching pecking order spot reported it was one of the historicly fast ones you get where you feel like your getting blasted out all the speed at the exit.
i found i could make fairly fast tubes and never go over 16-18 mph 22 mph was fast enough to get a big air going
wonder how many times Roy skips like a stone when he falls going 35+ mph i still Really want to see some of this on video must be amazing to see a guy go that fast.
went to roys site and watched a bunch of the video still did not see anything that looked faster then jogging speed
maybe a slow run on some of the fastest sections .
watch that youtube of ron ziebell and he looks like hes getting shot out of a cannon at the end of the 31 mph wave
Soul
I’ve tubed at 35mph before behind a boat, and it’s dang fast. Falling HURTS. That’s faster than slalom skiers go.
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Hold up, Tom/Roy.
You said in a post above that for a minute long ride, you only take the fastest second. This in and of itself makes your determination of speed absolutely flawed and invalid. Of the 60 (or more) data points you gather, you only choose to report one?
No it doesn’t.
We report the top speed achieved, a perfectly valid concept, the top speed does not occur in isolation, it is the highest reading in a series of readings which lead up to it.
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How do you think pharmaceutical companies would feel if they only had to report the best case scenarios in clinical trials? They would be in heaven, and every drug on the market would grant eternal life in their advertisements.
How do you think the police would feel if when caught speeding the driver objects that he wasn’t speeding because he was going slower 5 minutes ago ?
Quote:
Now, what about the rest of the readings for the ride? Give us a histogram of the readings throughout the fastest section of a ride (or even better, the whole ride), and we can then see what types of speed you are getting at.
I have news for you: Observing the data for the whole ride does not change the top speed reading at all.
Quote:
. By reporting the outermost outlier point, you immediately invalidate your analysis of speed. I would be tempted to more readily believe the average of the top quartile of readings (maybe even 90th percentile), but not an outlier point.
Incorrect: I am not reporting an outlier point. . . . .
you are mistakenly assuming that a peak speed reading is automatically a statistical outlier point, which is most definitely not the case. . . . a peak and an outlier are two different things.
Using an average of the top quartile of readings is ridiculous and will immediately cause grave inaccuracies in the peak speed reading.
Imagine if the sail trimmer on a racing yacht had to replace the live speed reading of the boat with an average speed . . . the result would be useless as an indication of the current speed of the boat, and useless for sail trimming purposes
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Basically, statistically speaking, you have no ground to stand on as far as speed readings are concerned if you are going to sort through the data and present it as you do.
Not true, gps readings are not statistical samples, you are applying an unsuitable model. . . .
To cut a long story short, the accuracy of GPS units has been proven, and in surfing terms has been shown to be accurate by Bill Barnfield and Terry Hendricks, both of whom have used gps units alongside Impeller based units and found that the gps results agree closely with the impeller based readings.
The length of the recording interval changes the peak speed reading slightly, as one would expect, however the most accurate possible readings are given by the doppler based ‘max speed’ function, which typically measures speed every 1/10th of a second.
I suggest that you post the same fallacious arguments to Terry Hendricks (MTB) who also uses GPS units to record surfing speed. . . . :
"How do you think the police would feel if when caught speeding the driver objects that he wasn’t speeding because he was going slower 5 minutes ago "
well put roy
Quote:
I tend to agree, a histogram or even an average speed would be the best measure.
No, that is ridiculous, top speed is an age old concept, you can’t just reduce everything to an average. . . .
.
Quote:
"How do you think the police would feel if when caught speeding the driver objects that he wasn’t speeding because he was going slower 5 minutes ago "
well put roy
Thanks Soul
Regarding your video comments, I think that it is very easy to mistake big, radical, and gnarly for fast. . . . and to mistake small, gentle and cruisy for slow. . . . we are so used to defining surfing in terms of waves size, danger, athletic move and the like that it tends to cloud our judgement when watching videos.
Also, please keep in mind that I do spend a lot of time going slowly. … .that’s just the nature of the break. . . it’s just a matter of hanging around waiting for fast section. . . . a lot of people seem to think that when I say i did such and such speed that I am claiming to be going fast at all times, and they seem to expect some kind of amazing action. . . . but speed is just speed, no more no less, and it can be achieved with a gentle slide or a spitting tube. . . the instrument doesn’t know the difference !
Cheers,
Roy
Mens slalom water skiing is done at 36 mph, at which point if you make all the bouys they keep shortening the rope. Womens is at 34 mph. But it depends on the sanctioning body. Current world record (IWFS) is 1.5 bouys at 43 feet off the 75 foot line, I believe.
When you are pulling like hell to get to the next bouy while crossing the wake, you are definitely going faster than boat speed, and wipeouts involve skipping like a stone and plenty of pain. I have been knocked out cold, and only the lifejacket kept me from breathing water and cashing my chips in. Knowing what 36+ mph is on a ski and barefoot, I can tell you that 36+ is faster than you think (Nathan knows this). 4-5" ripples become serious problems to be dealt with at that speed, and the water feels like concrete at the first impact/skip. I’m sorry, I just do not believe that from a paddling start (my guess: much less than 5 mph), reaching 36+ mph quickly can be done. It would require a mountain of a wave, or an engine. Try having a jetski/PWC with a speedo go along the same wave in front of you/beside you/behind the wave/whatever at 36+ mph and you will see what I mean as it pulls away at quite a rate. Even better, take the jetski/PWC out yourself and see how many waves you can hit 36+ mph on, and compare that feeling to your rides on a board.
I could be dead wrong.
JSS
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I could be dead wrong.
JSS
Nice to see that we are in agreement
The instrument reports the speed, end of story.
My boards are designed to handle that kind of speed on a wave
