Height Map Issue - It's making 4 of them Instead of 1

Hey guys, so I'm making a game for University, and I am TRYING (key word trying), to import this height map, however every time I do it, no matter what settings I change it always makes four of them to fill the terrain, instead of just one large one which Is what I need. Anyone have any ideas?

Here is a screenshot of what it looks like once I import it: http://i.imgur.com/S4iSKXL.png

Cheers,

Prophet