Is there a way to resize something relative to another object?

Hello,
I am currently trying to create a landscape that is the size of a real world location. I know the size of the real world location so I made a static mesh with the dimensions of the area and put it in the scene (the grey box below the height map). However my height map is not the same size as the static mesh. My question is would it be possible to make the landscape the same x and y dimensions as the mesh?

Screenshot: http://i.gyazo.com/01061d5b08b2886cb3262280053e25e5.png

Thanks.