myiW Current Conditions and Forecasts Community Forums Windsurfing Videos Buy and Sell Services
 
Hi guest · myAccount · Log in
 SearchSearch   ProfileProfile   Log in to check your private messagesLog in to check your private messages   RegisterRegister 
The every-minute-updating wind sensors

 
Post new topic   Reply to topic    iWindsurf Community Forum Index -> Southwest USA, Hawaii, Mexico
View previous topic :: View next topic  
Author Message
human_catapult



Joined: 20 Nov 2007
Posts: 372

PostPosted: Wed Sep 12, 2012 11:47 pm    Post subject: The every-minute-updating wind sensors Reply with quote

It looks like TI and Anita Rock have both been upgraded with sensors that give a reading every minute. I'm all for any kind of upgrades we get on IWS. kudos...

That said, I'm finding the readings at any given moment less indicative of actual conditions. For example the average wind speed one minute might be 17 then the next minute is 26. The moment when I actually open my browser would trivially make me believe two entirely different things about the actual current sailing conditions.

I'm wondering if averages over 5-10 minutes are actually more useful to us than the every minute readings. Is anyone else thinking the same thing?
Back to top
View user's profile Send private message
isobars



Joined: 12 Dec 1999
Posts: 13809

PostPosted: Thu Sep 13, 2012 7:38 am    Post subject: Reply with quote

The iW sensors around here seem to update in less than 15 minutes only if the average changes significantly. A couple of mph change = 15 minutes, but when we see an obvious drop or surge in the wind on the water, the sensor update may occur in one minute. That's useful in evaluating from afar whether and when and where it's time to drive. Each of those cliffs the wind falls over suggests a swim, big but brief surges imply a rigging frenzy for naught, etc. ... all factors in choosing sites and deciding when I'd rather mow the lawn.
Back to top
View user's profile Send private message
boggsman1



Joined: 24 Jun 2002
Posts: 3480
Location: at a computer

PostPosted: Thu Sep 13, 2012 9:42 am    Post subject: Reply with quote

human catapult....you are right. I was driving to Crissy Sunday, it read 21....a few minutes later it was 14, I bailed . Then 5 mins later it was 22. I should have just ignored the thing.
Back to top
View user's profile Send private message
windfind



Joined: 18 Mar 1997
Posts: 758

PostPosted: Thu Sep 13, 2012 10:46 am    Post subject: 1 minute averages: The story. Reply with quote

Hi human catapult,

For years to keep costs down most of our sensors recorded the average wind every 1 minute but only sent the average of those 1 minute intervals every 15 minutes. This saved us money and gave you useful averages on the wind graphs for each site but somewhat obscured the quality of the wind. Here are two different scenarios:

1. During a 15 minute period there can great steady winds with some 1 minute averages being 18 mph to and other 1 minute averages being 22mph so the 15 minute average you see on the graphs would be 20 mph.

2. Or there could crappy quality wind with some one minute averages of 12 mph and other one minute averages of 28 mph. But the average 15 minute average you would see on the graph would still be 20 mph despite the extremely up and down wind.

This is one reason why on some days a sensor seems very accurate when you hit the water and on other days a sensor seems way off.

I know the 1 minute averages look really busy and are hard to interpret at first. The key is to NOT to focus on the just the most recent 1 minute average. Rather look at the trend of 1 minute averages over the last 20 minutes or so. This will allow you to deduce not just the wind average but also the wind quality much better than just looking at the 15 minute average and peak gust and lull. If you use windalert.com (below) you can zoom into the graph to really see the wind quality.

Incidentally the one minute averages costs us more money. We are doing it for our America's Cup clients and only for Anita Rock, Pt. Diablo, Alcatraz, Point Blunt and Aquatic Park. For a tactician on one those boats 1 minute interval reports are invaluable.

I expect we will revert those sensors to 15 minute intervals after the 2013 AC is over which will give you something to look forward to if you can to adapt to the information overload.

If things go right we will have some awesome new sensors in the Crissy field area by the 2013 season.

Hope all of this helps.

Mike Godsey



ZZ025809E9.jpg
 Description:
 Filesize:  393.57 KB
 Viewed:  2166 Time(s)

ZZ025809E9.jpg


Back to top
View user's profile Send private message
surftex



Joined: 26 Aug 2008
Posts: 24

PostPosted: Thu Sep 13, 2012 11:53 am    Post subject: Reply with quote

Hi Mike,

I, for one, appreciate the additional information we get from the 1-minute updates. I will be sad to see them go. However, they do increase the cognitive load in evaluating the wind at a glance.

Just a couple of ideas for down the road:

1) Incorporate standard deviation (or some other measure of variance) into real-time measurements, perhaps over a 5 to 15 minute window. "Gust" and "Lull" used to be pretty useful here, but they are just as jittery as the average with the 1-minute updates. Similarly, gust and lull could be clamped over a 5 to 15 minute window.

For standard deviation, you wouldn't have to report a numerical metric, just some visual cue as to the spread. This would help to identify crappy strong wind at a glance (as referenced in your post) without spending the time to load a graph and zoom in on it.

Along those lines, anything you can do to reduce the cognitive load in evaluating the wind is helpful. You could display 5 to 15-minute rolling averages in any list-view of sites, while still showing real-time measurements when looking at a specific site or graph.

2) Incorporate a direction distribution (like the compass rose in the "Wind Statistics" panel for a site at WindAlert.com) into the real-time measurements. Crappy wind is often shifty rather than gusty.

Best regards
Back to top
View user's profile Send private message
human_catapult



Joined: 20 Nov 2007
Posts: 372

PostPosted: Thu Sep 13, 2012 12:06 pm    Post subject: Reply with quote

Thanks for the explanation.

I typically look at IWS on my phone periodically while I'm *ahem* driving to the spot. The primary pages I use are the "Wind Obs Map" and the "Wind Obs Summary".

Usually I just glance at the summary to make a decision about where I want to sail that day. As a windsurfer you know that the difference between 17 and 21 is huge, but I find that anita rock and TI both oscillate between these numbers with much frequency. I hardly ever look at each location's graph. I usually just look at the average on the summary then make a split second decision based upon that.
Back to top
View user's profile Send private message
isobars



Joined: 12 Dec 1999
Posts: 13809

PostPosted: Thu Sep 13, 2012 12:40 pm    Post subject: Reply with quote

human_catapult wrote:
I usually just look at the average on the summary then make a split second decision based upon that.

Ditto. People asking me for gusts and lulls are frustrated by my shrug and "Dunno. Didn't look." First, it affects my sail size only if the holes and/or gusts are extreme and frequent. Second, all the numbers usually change significantly, sometimes dramatically, by the time I get rigged and dressed. Third, I'm going to rig big anyway for my first session to reduce the odds of having to slog or swim back after a reality check. Overpowered beats underpowered ALL to heck for that purpose, and decimal points are pretty useless for all three reasons.

If the (wind-generated) swell looks appropriate to the wind's average speed, the wind is reasonably steady. If not, the wind either recently changed or is constantly changing. One could almost say that swell size indicates the average wind speed and whitecaps indicate the wind speed at that moment.

Board, fin, and sail size are also often dependent on many other factors, such as time of day, wind shadow, sea state, and the penalty of rigging too small to plane.

All that said, I'd very much appreciate more frequent updates *IF* it adds useful information. At present, with our local iW sensors, I believe that no update means the numbers haven't changed. If that's correct, I don't need to see 22G30 every moment.
Back to top
View user's profile Send private message
rigatoni



Joined: 25 Feb 1999
Posts: 331

PostPosted: Thu Sep 13, 2012 7:56 pm    Post subject: Reply with quote

thanks for the tip on zooming in. Those graphs are impossible to read in "normal" mode.

Also-this time of year pay attention to the gust number at Crissy or better yet ignore it completely. Wind in September can be reading 10 knots lighter at Anita than another 50 yards out.
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    iWindsurf Community Forum Index -> Southwest USA, Hawaii, Mexico All times are GMT - 5 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You can attach files in this forum
You can download files in this forum

myiW | Weather | Community | Membership | Support | Log in
like us on facebook
© Copyright 1999-2007 WeatherFlow, Inc Contact Us Ad Marketplace

Powered by phpBB © 2001, 2005 phpBB Group