Re: Ground limit and 3D model

Sam Heyman wrote:
> I have now nearly finished implementing our project UAV "Manta" in 
> Flightgear and am very satisfied with the result.
> 
> There is one thing though which I am not quite sure about and that is 
> the position of the 3D model. It seems to be positioned correctly and 
> flies pretty accurately. The problem, however, is when I start the 
> flight on the runway the aircraft is placed right on the edge, rather 
> than on the zebra-crossing...
> It also has a tendency of going "underground" easily.
> 
> Should a correctly placed 3D model stay above ground at all times?
> Does this mean that my 3D model is offset from the FDM coordinates? (the 
> model is only 2.2m span, so is much closer to the runway).

This sounds as if you have the X and Y offset switched somewhere, 
causing the aircraft to be modeled th the right instead of forward.

If the gear contact points are defined (which they should be since it 
does stay on the runway) then these contact points clip the plane to the 
ground.

 > Where is the center of the FDM coordinates placed when you start the
 > flight on the  runway?

In case of JSBSim there is on imaginary center (0,0,0) which could be 
placed at one of the known locations of the aircraft.

Erik

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