[Flightgear-devel] multiplayer input

[<ken...@co...>]

I am working on a program to convert ecef (Earth Centered Earth Fixed) position and velocities, and aircraft yaw, pitch and roll to the FGExternalMotionData structure defined in mpmessages.hxx.  This is fun!  
1. Every input variable is commented with relation to the earth centered frame.  What specifically is the coordinate frame.  Is it ecef ?  I've been down too many rabbit holes already.
2.  I just want someone to validate my conversions.  
     a. I am taking the ecef position and converting it to lat lon then converting that to a quaternion.  I then take the yaw, pitch and roll and convert that to a quaternion.  Then I multiply the 2 values to get the new rotation.  That will be converted back to an Angle Axis which is the orientation value in the FDExternalMotion Data struct.  
    b. LinearVelocity is the xyz velocities I already have if I don't need to translate ecef into another coordinate system.  
    c. The Acceleration will be the delta from last to present velocity vector.  
    d. The angular velocity and accelerations are the euler angles for the aircraft? (rate of change in radians on each of the three axis)
3.    The T_PositionMsg has the orientation as an angleaxis. How do you code the angle into the axis length?

any help would be greatly appreciated,

Ken