From: skybuckflying@gmail.com   
      
   The following math is required to make UFO Alert Tool really accurate:   
      
   1. Ray-tracing a spheroid.   
      
   2. Great Ellipse distance between two points.   
      
   3. Shortest Distance from a point to a Great Ellipse.   
      
   These math problems are due to the Earth being flattened by gravity.   
      
   For now I will try to proceed with an spherical Earth but this will be less   
   accurate.   
      
   The preferred math is with vectors so it can handle x,y,z positions returned   
   by the ray-tracer.   
      
   This special math is needed for visualization of arcs across the Earth.   
      
   Bye for now,   
     Skybuck.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)