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isobars
Joined: 12 Dec 1999 Posts: 20936
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Posted: Tue Nov 20, 2012 5:31 pm Post subject: |
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I've sailed there, seen the rocks, heard them cursed. The CA sailors who claim the rocks don't exist are a whole threadful of angry left coast wave sailors who ran out of "You're a racist" insults. |
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keycocker
Joined: 10 Jul 2005 Posts: 3598
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Posted: Tue Nov 20, 2012 6:24 pm Post subject: |
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Jumps, speed, and other worlds records are a regulated thing.
They have been going over fifty knots with a speed gun in the Gorge from years ago, but the world record just passed fifty recently.
Same with jumps, that event in Hookipa doesn't count.
The GPS records are a lot higher than any official speed.
The reason that require a nearly unaffordable jury with sealed instruments should be obvious. When I handed out GPS at the Navman Speed event, one kid noticed that the longer they lay on tne desk,the faster they said the event tent was flying across the beach.
the one he grabbed said 6knots. Mark said just reset them to zero as they take them out, but the kid wanted that unit anyway. |
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boardsurfr
Joined: 23 Aug 2001 Posts: 1266
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Posted: Wed Nov 21, 2012 6:37 pm Post subject: |
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keycocker wrote: | The GPS records are a lot higher than any official speed. |
That may well be true for old (non-doppler) GPS gear, but the gear currently recommended on the GPS speedsurfing sites (Locosys GT-31 in doppler mode) is quite accurate. For example, Antoine Albeau's record from today over 500 m was 52.05 knots measured with the official equipment, and 51.96 knots measured with GPS (see http://www.gps-speedsurfing.com/default.aspx?mnu=user&val=111117&uid=412). His 5x10 second average, which is usually used for GPS speed, was 52.13 knots, also very close. The same is true for the other sailors in Lüderitz that post on gps-speedsurfing.com.
He did not submit this as an "official" GPS record; if he had, the GPS numbers would have gone down a bit (due to subtracting error margins, I think). But either way, the GPS results are almost always within 0.1-1 knot of the official (gate) measurements.
However, if you put on a Garmin Foretrex or something similar, and sail a few days, chances are that the Garmin will tell you that you hit 40 knots, when you actual top speed was less than 30. I've seen it happen several times to different sailors. |
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MindWaves
Joined: 16 Jul 2000 Posts: 38
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Posted: Fri Nov 23, 2012 3:48 pm Post subject: GPS speeds |
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The problem with consumer GPS is that it only gives you a location once per second, and in high dynamic sports like Windsurfing, a lot can happen in one second. In addition to the slow data rate, the precision is roughly 5 meters, so given those two variables, its no surprise that speed readings from GPS systems can vary wildly. Especially when compared to a speed timing/trap system.
The Locosys has a similar GPS as to what we have in the XensrCase, but in addition to the GPS data, we also mix in motion data to give data at 400 times per second, giving amazing precision to the data.
The whole goal here is to offer not only amazing precision in speed, but also give you 3D location data for things like jumps, tricks, etc. |
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almineev
Joined: 25 Apr 2010 Posts: 23
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Posted: Sat Nov 24, 2012 3:59 am Post subject: |
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boardsurfr wrote: | However, if you put on a Garmin Foretrex or something similar, and sail a few days, chances are that the Garmin will tell you that you hit 40 knots, when you actual top speed was less than 30. I've seen it happen several times to different sailors. |
Carry two Garmins? and average them out in software post processing. |
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nw30
Joined: 21 Dec 2008 Posts: 6485 Location: The eye of the universe, Cen. Cal. coast
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Posted: Tue Nov 27, 2012 12:25 am Post subject: |
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How high do you need to go?
Just wondering. |
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techno900
Joined: 28 Mar 2001 Posts: 4172
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Posted: Tue Nov 27, 2012 9:42 am Post subject: |
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Quote: | boardsurfr wrote:
However, if you put on a Garmin Foretrex or something similar, and sail a few days, chances are that the Garmin will tell you that you hit 40 knots, when you actual top speed was less than 30. I've seen it happen several times to different sailors. |
I have carried a Garmin Foretrex 201 for the last 8 years on EVERY windsurfing outing, which is over 600 days of windsurfing. Only once has it given a bogus speed (105 mph). The rest of the time it has been exceptionally consistent. I also record all the data after each outing.
I wear it on an arm band inside a Aquapac (which as had a few leaks repaired). |
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girsang
Joined: 16 Jun 2000 Posts: 52 Location: San Francisco
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keycocker
Joined: 10 Jul 2005 Posts: 3598
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Posted: Wed Jan 09, 2013 12:11 am Post subject: |
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I have never had a chance to speak to someone with your considerable experience in using a Garmin. Does it show speed at times while sitting still on the table like the Navman we used in the Navman Speed Series? |
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cbknap
Joined: 03 Jun 1997 Posts: 373
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