function  getLatitude(scr_y){ 

   scr_y = scr_y - getMapImageOffsetTop();
   var map_image = getMap();
   var drag_m2 =  getM( BY2IY(scr_y,map_image),  imageYMin(), imageYMax()); 
   var drag_m3 =  getM( BY2IY(scr_y,map_image),  imageYMax(), imageYMin());  

   var n2 = drag_m2 *  mapYMax();  
   var n3 = drag_m3 *  mapYMin();  

         // this is an override for moveing off the map to the south 

   if(drag_m2 <= 0){  
     return  mapYMin();  
   }  
  
       // this is an override for moveing off the map to the 
	   // 
   if(drag_m3 <= 0){  

     return  mapYMax();  
   }   
  
   return (n2+n3)/(drag_m2+drag_m3);  
 }