Windfield simulation includes thermals. Please take a look into the
subdirectory "./thermals/" if you are interested.

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Changelog:
  2012-10-28: several updates later..
  2005-10-14: first version


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(2012-10-28)
--------------------------
Windfield is hardcoded for built-in scenaries only.
For model-base scenaries a couple of options exists to estimate wind
from the terrain height profile.

The effect of wind turbulence has been added, based on Dryden digital 
filter model as specified in MIL-HDBK-1797. Only the low-altitude model
is implemented since it is valid up to 1000ft.



(2005-10-14)
--------------------------
Windfield is hardcoded, which means that (apart from thermals) it is not
worth describing it. Please take a look at windfield.cpp.

What needs to be done
---------------------
 - random variations in direction and strength
 - turbulences (the FDM needs work in this case, too)
 - terrain dependend windfield


How does "Slope Soaring Sim" do it?
-----------------------------------
enviroment.*
wind_field_generator.*
There are some methods "*wind_from_terrain", called from enviroment.cpp.
filtered_separated_wind_from_terrain
How does "runtime" work? Is it Velocity Environment::get_background_wind_from_terrain(const Position & pos,
                                                       bool thermal) const?


How does "JSBSim" do it?
------------------------
src/models/FGAtmosphere.cpp includes different models for turbulence. No
windfield simulation based on terrain. Maybe this is done somewhere else?
There must be a call to void SetWindNED(double wN, double wE, double wD)
somewhere. But I guess that this is in FlightGear, as JSBSim doesn't know
anything about the terrain?