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 Wind effect by height « View previous topic :: View next topic » 
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PostPosted: Sat Nov 01, 2008 10:18 pm    Post subject: Wind effect by height Reply with quote

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Joined: 09 Mar 2008
Posts: 4
Location: CT USA

The program may already do this. However, when wind is added. Is this assumed to be at the ground level? If so, There is a change ( increase) the higher you go.. The wind blows faster at higher altitudes because of the drag of the surface. Also.. Do you have the algorythm for that?


Mike B
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PostPosted: Sun Nov 02, 2008 2:19 pm    Post subject: Reply with quote

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Joined: 10 Apr 2007
Posts: 57
Location: Ravensburg, Germany

Hi Mike,

no sorry, we don't have that at the moment and it is not yet on our list for 2.0.

However, we may consider to include it if we get an evident model for it.


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PostPosted: Tue Nov 04, 2008 10:30 pm    Post subject: Re: Wind effect by height Reply with quote

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Joined: 09 Apr 2007
Posts: 105
Location: New Jersey, USA

To deal with this, I had to forget about golf and go back 3-4 decades when I was deeply involved in a sport where the wind gradient with altitude is a critical issue: sailboat racing. Yes, I was just as big a technology geek about that as I am about golf. My favorite book at the time was C.A. Marchaj, "Sailing Theory and Practice" -- which is even more technical than it sounds.

I dusted off my copy of Marchaj and found, on p.107, the following passage:

"The speed of the true wind increases with the height above the sea. At the surface of the sea the motion of the air is retarded by friction, and this procss is continued upward through successive layers... The rate of increase of the wind speed, the wind gradient, depends on the weather conditions and the state of the sea. Figure 71 shows a typical wind gradient curve for the average sea conditions over open water. In the proximity of land or on inland waters, the shape of the curve can be quite different."

Now what happens if we try to take this to a golf course? The terrain variation is way more complex than the sea variations that Marchaj already says creates very different height profiles for wind speed. Trees and slopes make it even harder to characterize the wind gradient for a golf course than a sailing race course.

So I don't think you'll see this folded into TrajectoWare Drive any time soon. It's just too hard to characterize in any consistent way.

Which brings me to... As a sailboat racer with a good record, I am always amused watching golfers (even the pros on TV) tossing up grass to see what the wind is going to do to their ball. Unless they have the sort of knowledge of wind that inland sailboat racers have, they don't know how futile that is. Far better to look at the tops of the trees and try to determine something from that. Yeah, it's less precise; it will tell you direction to maybe 45 degrees at best, and speed to 10mph. But grass or cigar smoke at ground level, though more precise, often gives you a completely wrong answer. For instance, you may be able to interpret direction to 10 degrees; but, if you're in the influence of some trees, that answer is likely to be 180 degrees off what the ball will actually experience for most of its flight.

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