& btmapelev()
 
  Syntax: btmapelev(<MapDB>,<x>,<y>)
 
  This function returns the elvation of the specified hex on the 
  specified map. This can be a number between -9 and 9. Negative 
  numbers denote water, positive may be any other terrain.
 
  Error Messages:
 
  * If <MapDB> is not valid the function will return #-1
  * If <x> <y> are not numerical the function will return #-2
  * If <x> <y> are outside the boundaries of the map the function 
    will return ? 
 
  Example: 
  Given that #62 is a map of 50 x 50
 
  > think btmapelev(#62,5,9)
  1
  > think btmapelev(#62,10,10)
  -3
  > think btmapelev(#62,27,61)
  ?