How fast is fast, and then even faster.......

Speed seems to be a pretty big thing now, GPS, speed events, racing. All very exciting stuff, and a great avenue for a washed up old skool kiters like myself!

I would like to open the claiming arena with some claims from back in 2006,

Stock production gear, 2006 Shockwave 9m and SOL 133. GPS reading 33kn. Altona, Vic.
Also stock production gear, 2006 Kitewave 5'2" and Torch II 12m. 31kn. open ocean.
Custom Jimmy Lewis Myth 100cm, Torch II 12m farking quick until I stacked and broke the GPS, fastest I've ever been, estimated 90kn.

I haven't done any GPS since, because the GPS is broken, but kindly Wind Surf 'N' Snow has offered to get me back in the run for the 50kn barrier, Thanks SAMBO!

Please tell me your tails of the need for speed!

JB

I too must be a washed up kiter as i love the speed thing now. I just have got to get out in more wind to push the speeds up. I think in 20 -25knts wind anything more than a low 30 has to be a bit special.

Just need that constant 35knts SW at sandy point and the record is mine ( ha ha ha (not sure how to do an evil type of laugh in text))

Not trying to steal any thunder but, the nicotine afflicted dwarf is correct...

the company I work for find 16 inch holes in the ocean floor with differentially corrected GPS systems. You couldn't find your own arse in a sleeping bag with the things (GPS) you strap to your wrist... so any SOG (Speed Over Ground) calculations by said devices are next to worthless.

I wont enter into discussion about precision and accuracy in this forum, I suggest you get a degree or (better still) look it up yourself, but suffice to say that wrist worn GPS devices do not have the accuracy (over the range of measurements they are commonly used) to derive a real measurement of speed. Period, full stop, bla bla, yawn.

(You could strap one of those things to a coca plant and you'd swear Ben Cousins, Brittany Spears and Kate Moss were all chasing after it, coz you're just as likely to see it doing 120kmh while it's still firmly rooted in the ground!)

What about statistics though chaps? Yes my Garmin 201 could be telling me I'm here or next door, but when it records a thousand points in a couple of hours and I start doing statistical calculations on them, does that not count for anything? Especially with data cleansing beforehand.

That's a very interesting sentence you've bolded there Azza, permit me to retire for the evening and do some follow up research on the morrow.

GreenPat,

if the range is short, say 100m, then the error factor of the two end points is +-15m each (being a commonly accepted accuracy, provided everything is working, so it might be more or less in actuality. You will see 100m accuracy commonly quoted too.)... that gives you a 30m error factor for the 100m, that we know to be 30%, which is not greatly accurate.

Over a longer range, say 1000m, we can reduce the error factor, to say 30/1000 or 3%... getting better. (That is provided we are dealing with +-15m not +-100m accuracy.)

This is all provided everything works as designed... now you have to start considering other errors like quantisation, sampling, multipathing, propagation, and timing errors, etc etc.

Because the GPS system is a US military asset, you only get to use the civilian (read: hobbled by design) component of the system.

It's still lots of fun to use these devices, but they're not that accurate as to say "I did 42knts on one 100m leg of my last 1km run" and be taken seriously everywhere you say it.... if you know what I mean.

GPS needs a local base station, or the US military codes to be more accurate.

It's great to see some friendly competition and socialising though, and that's what it's all about.

Yes Azza, this we know, but the speeds published on gps-kitesurfing.com are calculated from no less than 25 different points. This is what I'm saying about statistics. If the variation on each of these is +-15m and follows anything like a normal distribution, then the accuarcy of an average of 25 of these readings would probably be much higher than +-15%

Re GPS, Later in 2008 we will have a GPS system that is very accurate as the speedo wearing EUROs are doing there own GPS system because the American GPS system sux.

Costs is only 3.6 BILLION.

"Galileo's civilian signal will also give locations accurate to within one meter (one yard) -- a significant improvement on that offered by the GPS system."

Full story here:

edition.cnn.com/2003/TECH/space/05/27/europe.galileo/

Azza!

are you just a little bored?

Next question: How much more accurate, do the filtering programs, make these results?

Good questions Tony,

(1.) I am both a little bored and a little drunk... but, hey, it's 39 degrees Celsius here in Perth today and there is stuff all else to do (kite-wise) because of the weather system.

(2.a.) The filtering programs do not make the measurements more accurate, the only way to do that is invest in more accurate equipment... and that is too expensive for recreational use.

(2.b.) The filtering software does/can, however, remove any data that is obviously erroneous... that is, a reading that would appear as a dramatic spike on a graph... once removed that data does not ill effect the other data in the set. That does have the effect of making the data set more accurate, but not the individual measurements themselves. It sorts the seed from the chaff, if you like.

(2.c.) The other thing the filtering software might do is give you a mean/average of the filtered data... that is, it gives you a precise answer from a group of readings... it will give you precision.

(2.et al.) This link gives a good definition/analogy of accuracy vs precision. http://honolulu.hawaii.edu/distance/sci122/SciLab/L5/accprec.html
What this analogy doesn't cover well is the issue of measurements that are not necessarily within a clearly defined field, like a dart board. Accuracy applied to GPS is more akin to throwing the board at the dart, to use the same analogy... now, obviously, sometimes you will miss completely and GPS does too. So filtering software removes those misses from the final equation. Still using the same analogy, for one position, if we have a group of readings we must overlay the area of the dartboard over the bullseye of each reading... so for two readings you will get some kind of figure "8" pattern and for five readings it will be something like a demented Olympic rings symbol. The area covered by the dartboards is your area of accuracy, the software will average those positions to give you a precise "mean position" and the accuracy is the whole area covered by the dartboards. (It's messy, I know.)

The Garmin Geko 201 manual states the accuracy as "<15m RMS", and it says "subject to accuracy degradation 100m 2DRMS under the U.S. DoD-imposed Selective Availability program." The S.A. program has now been terminated, but don't expect full compliance with "<15m RMS" all the times, due to PRN outages/maintenance and DoD usage... yes, they still like to spy on people and blow sh1t up etc. So less than 15m RMS is the best you will ever get from one reading, and speed is calculated from at least two readings and a time factor... so less than 30m is the best you will get for a speed calculation based on only two readings. (Now that is purely accuracy not precision.) Introduce three readings and your error is now between less than 30 and less than 90m, dependant upon where you third reading is.... now add four, five, etc etc.

Like I said before,
Accuracy costs money, how precise can you live with?

For a couple of hundred dollars, not thousands or tens of, you can have lots of fun zipping around and going fast and being able to say "I did XXknts within this much reasonable certainty." (Of course you can leave out the "reasonable certainty" clause because it is largely moot within our degree of fun... isn't it? )

Way too much information.
Looks like someone’s talking out of his Azz once again.
Would have thought that ‘nip tuck’ job on the pie hole last year would have stopped the overflow of drivel.
Obviously not.
Blame it on the alcohol I say !