take a look and let me know if someone can have a look at my tracks to see if i can get the 40 but i dont think so.

gpsteamchallenge.com.au/sailor_session/show?date=2010-08-20&team=27

Gutsy effort to all of you.

PM 'd you Izaak

Tom Chalko's Fourier program will get a 40.276 for you if you are desperate but if everyone else is calculating using Realspeed, KA72 etc it does defeat the point a little.

http://sci-e-research.com/Fourier.zip

thanks for that but i will leave it at that till i get it though real speed doppler or KA72.i hope it wont be long.

In a peaky run like the one you did at Henty I think Tom's Fourier program may be more accurate as the Fourier program blends the speeds in a more natural "real world" way whereas the Realspeed joins the instantaneous recording points with a straight line. But then again when you look at the points on Tom's graph it does also look like it adds changes which are not there. Tom shows a small drop in speed at 33 on the acceleration but the actual recorded points continue to rise. Doesn't look like a best fit curve to me.



At a place like SP where you plateau for a fair way at your top speed the straight line in RealSpeed probably makes very little difference.

GPS-Results uses the GPS-SS approved method to integrate the curve. Toms Fourier method is not approved. In GPS-Results it uses the Cubic Spline method by default for 10 sec and 20 sec. You can switch the options to trapezoidal or quadratic spline for 2/10/20 sec. Worth a play if you have the program. If you don't, send your track to me and I will send you the results.

andrew i will send the track to ya and see what ya think,im not too fussed what the out come is.

Izaak, Gps-Results is a nice program and you can have a free trial period.

You find it at www.gps-speed.com

Cubic spline and Rectangular give the same result (it does not integrate the 2 sec on this filter setting) in GPS-Results: 40.364+/-0.301
Note the correction factor. Even if you take this off you get a 40+ two sec.
This result of worked out from 2 data points.
Trapezoidal (the default in most versions of RealSpeed) uses 3 data points and in GPS-Results it gets 39.902+/-0.306. Note that this is +/- 0.306 so your real speed could have been as high as 40.2 even with this system.
Quadratic integration also uses 3 data points and gives 40.170+/-0.314.
I think you should be confident that in this case there is a very high probability that you did 2 seconds over 40 knots!

I think there's a high probability that you went faster than I've ever gone, and I'm very jealous!!!

We have had a couple of instances where people have tried to use different programs and methods to bump up their scores, and it always ends badly. For me as well as them!

In all seriousness, you're best off with just going by what your usual program gives you. That way you keep your integrity, no-one will accuse you of cheating and you get to sleep at night.

You should be immensely proud of that special day, and I know that next time conditions are right you're going to smash that 40 knot barrier into tiny little pieces!

yes thanks for the help guys, i will leave it at that.but will say to others ive done 40 im am very pleased with what i did any way

pity it still isn't a 2 sec average in Doppler cause thats what we use on GPSTC so why not make it 3sec on it.

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izaak said...
[>>>>
pity it still isn't a 2 sec average in Doppler cause thats what we use on GPSTC so why not make it 3sec on it.

Not sure what you mean here Izaack, but if you're querying why 3 points are used to calculate doppler 2 seconds. The answer is fairly simple, each doppler data point is close to instantaneous, so for a second, you need 2 points, the start and the end of the second. For 2 seconds you also need the start and the end, this means 3 points. So it's quite possible you actually went a bit faster than your peak speed, a point in between the 2 fastest readings

Trackpoints only needs 2, because each point is the distance travelled in that second.

next stop 500m NM would be great if there were more than 2 places in the world where this was possible, but most countries can post a respectable 500m. Even if it involves aeroplanes. Great effort seeing 40 on the dial. I remember when I first did that and was jumping for joy (despite the fact it was probably a spike on mine ). Hopefully it blows at speed fortnight. Will catch up for a beer (with your old man )

Congrats Izaak, you give me hope.
I'm curious as to what gear you were on, if you don't mind me asking.
I'm currently trying to buy some speed gear myself, (IF ANYONE WOULD ANSWER THEIR MAIL !!) so I'm keen to hear, though I am pretty settled on what I want.

forget i said that decrepit.we may have some cranking NM though summer a henty we think its the right length.

kenho i was using my JP speed 45, Neilpryde RS Racing EVOII 4.7 with a ka lockwood asymmetrical 20cm fin. and wow what a combination !

Neat !!
I'm looking at a similar size board and fin, though will probably need larger sails. I'll stick to a symmetrical fin, as I have fast port tack places to sail too.
It's been too long since I went scary fast.

I had a sail on the 45 recently and it needed a lot of wind with my 78kg and a koncept 5m to get it planing. Spent a lot of time swimming on that gusty day. It was certainly quick but I could not get enough use out of one here in WA to justify a purchase.

Run a bigger sail.
I'll start with a 6.4/6.6.

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lao shi said...

I had a sail on the 45 recently and it needed a lot of wind with my 78kg and a koncept 5m to get it planing. Spent a lot of time swimming on that gusty day. It was certainly quick but I could not get enough use out of one here in WA to justify a purchase.