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How is wind speed calculated?


asp22
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Does anyone know how wind speed at a given altitude is calculated?

 

In an attempt to discover this, I created 3 wind profiles in the mission editor and took readings at various heights using an A-10C.

 

all directions set to 0

Profile 1, ft - kts

33 - 10

1600 - 21 (automatically set)

6600 - 0

26000 - 0

 

Profile 2,

33 - 0

1600 - 0

6600 - 20

26000 - 0

 

Profile 3,

33 - 0

1600 - 0

6600 - 0

26000 - 20

 

I've attached a plot showing the speeds at various alt for the three profiles. I've discovered that between 33ft and 1600 ft a power law with a coefficient of 0.194 seems to be used, The rest looks like some sin/cos flavour but i can't quite get them to fit. If anyone has looked into this and knows the magical formulas i'd be interested.

 

 

Thanks,

 

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Update: I have managed to produce a reasonable model and have stuffed it into an excel sheet I've also added a screen capture to give you an idea of what to expect should you choose to download it.

 

I hope that the use is straight forward. You use the sheet 'Settings' to plug in values and 'Results' has the calculated values provided in a table. The sheet 'Maths' has, well, the maths.... apologies if you take a peek inside here; my excel skills need a bit of work.

tool_sneak_peak.thumb.png.e9c3d9691925fc374a92dad3889cacc9.png

wind and temperature estimation tool.zip


Edited by asp22
fix broken attachment
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razo+r. I think there is a misunderstanding. I understand that it is possible to change wind speeds at certain altitudes. I'm interested in the model that DCS World uses to create a wind profile from the 3 values specified in the mission editor.

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Good question, I'd be interested as well.

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wind direction is always where it is coming from. the ATC just takes what it is set at and reads it back.

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Does the mission editor indicate air speed direction from where it's coming or where it's going?

Also how does ATC indicate air speed direction?

Mission editor and briefing shows the direction the wind is blowing to.

 

ATC on final gives the direction the wind is blowing from.

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What about the 'briefing screen' I take it that it and all other indicators in the sim are where the wind is blowing from.

The briefing screen also shows direction to. AFAIK the only thing that gives the direction the wind is blowing from is ATC during the landing clearance.

 

You can check it by placing a windsock. :)

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Looks like this thread has gone on a bit of a tangent. :)

 

What grunf has said is true;

mission editor: direction the wind is blowing towards (eg. 0)

briefing: direction the wind is blowing towards. (0)

In flight: direction the wind is coming from. so it is coming from 180 and trying to push you towards 0.

 

Regarding the wind profile, I think that sin/cos wave bits are modelled by Bezier curves. I've had a quick play and i can get a reasonable fit. I'll test it out to see if it can predict other profiles and report back.

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Bezier curves seem to work. I used a cubic variant which gives a reasonable estimate; I wonder if a higher order improves things

 

I created the following wind profile and took readings from 20 to 30000 ft

 

33ft - 0 deg - 10 kts

1600ft - 0 deg - 21 kts

6600 - 90 deg - 30 kts

26000 - 180 deg - 40 kts

 

I then used the model to estimate the same profile. Results are attached. I've not corrected for the magnetic variation but results seem pretty good as a first approximation.

 

I'll upload an excel sheet as soon as I've tidied it up.

wind_profile_estimate.thumb.png.e5cabc18a601e36fde7a3e37ba3d3a7d.png

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I've updated the first post to include the excel sheet of the model.

 

I got an empty file when I downloaded the Excel sheet.

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