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List:       flightgear-devel
Subject:    Re: [Flightgear-devel] Local Weather menu structure: Wind settings
From:       thorsten.i.renk () jyu ! fi
Date:       2012-01-31 7:58:44
Message-ID: 33367.130.234.144.109.1327996724.squirrel () webmail3 ! cc ! jyu ! fi
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> I just faild to set the wind speed and direction in the new weather menue
> structure (up to date next-branch). My intention was to set the wind
> profile
> from ground up to 3000ft.
> Hence I used the Basic Weather menue and set the desired values in the
> table.
> But I found that I got the wind speed and direction from the Advanced
> Weather
> Menue instead. Is this a bug/feature or am I simply to stupid to set the
> values correctly?

Not sure what exactly you were trying to do. When you run Advanced
Weather, it always uses its own wind model - it can't know what you
entered in the Basic Weather config dialog and it doesn't care - we're not
so far along the road to a merged weather system (if you were running
Basic weather and it was ignoring its own config, that'd be a bug though).

Advanced Weather has a few wind modes - constant (wind is the same
everywhere), constant in tile (wind is the same in each chunk of 40x40 km,
but may change between tiles), aloft interpolated (wind is interpolated
based on the values entered in the wind dialog which is visible when you
press 'show winds' and aloft waypoints (wind is interpolated based on a
set of vectors both in altitude and in position - this is *very*
cumbersome to enter manually and intended to run with online weather).

Even the aloft interpolated modes don't allow you to select an arbitrary
wind profile though, the low altitude interpolation altitude values are
always 0, 5000 ft and 10000 ft (this choice made following advice from
TorstenD who had plans to get online aloft winds automatically in this
format, something which isn't implemented yet), so you can only have a
linear profile between these altitudes.

The system doesn't allow you to specify wind conditions in the boundary
layer, because it wants to compute them itself. You get a boundary layer
which adapts to terrain roughness and local elevation, for instance there
is no boundary layer slowdown of winds at mountaintops, and significantly
less on upper mountain slopes than on the ground (which is somewhat
important for ridge lift to work properly), boundary layer slowdown is far
less pronounced over open water than in mountain terrain,... I suspect you
were interested in specifying especially this region? In case you  want to
do something to the boundary layer computation, you'd have to dig into the
code, this can't be done from config.



Hope that helps.

> BTW:
> I'm totally impressed by the capabilities of the weather system,
> especially
> for glider pilots. I must admit that the weather system is a big
> motivation
> for me to keep up the development of a hangglider for FlightGear. Up to
> now the results are very promising. Soaring feels very realistic!

Thanks.

There's a lot of real life glider flying experience behind the convective
cloud system and the thermals :-) If I find the time (which doesn't happen
too often) I enjoy going cross-country with the ASK-13 very much. Like in
real life, there are all sorts of surprises which can happen, and I always
find mountain-soaring very exciting. Still need to implement that wave
lift model at some point...

Cheers,

* Thorsten


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