The heightfield load operator which contains your loaded GC2 terrain should show you the size of the loaded terrain.
That operator is connect to a heightfield shader and should show you the coordinates at which the terrain is placed.
By default this is 0,0,0 at the lower left of the terrain.
Create an imagemap shader and set it's position to the same coordinates as the heightfield shader, so 0,0,0 and lower left in this case.
For size enter the value in metres as shown in the heightfield operator.
Now they should align perfectly.
