Can you get the global coordinates of a collision event?

Why are event.x and event.y always 0 here?

local function myCollision( self, event )  
 print("event occured at x: " .. event.x .. ", y:", event.y)  
 return true  
 end  
  

What is the best way to get the x,y of where a collision happened? [import]uid: 52127 topic_id: 11315 reply_id: 311315[/import]