2D array tile map diemsnions from Isometric map

Can anyone suggest a formula to find the dimensions ( width and height ) 
of a 2D array tile map in terms of tiles from an isometric map? The 
Isometric tiles are typical 2:1 diamonds and the width and height of the 
isometric maps vary because they are randomly generated. These isometric 
maps are not 45 degree rotated squares maps, they are rotated 
rectangles. For example I have the isometric map on the left, but I need 
to create the 2D array on the right, which turns out to be 3x5.

   /\         _____
  /\/\       |_|_|_|
/\/\/\      |_|_|_|
\/\/\/\     |_|_|_|
  \/\/\/\  = |_|_|_|
   \/\/\/    |_|_|_|
    \/\/
     \/

Thanks