Hi everybody

I am playing around with geocontrol and a world of mine I want to create, so far I've followed Hoddimirs tutorials which are really good, and I have successfully created a good heightmap (4096x4096), but i realized it was simply too small. So I wanted to make it bigger, but the problem is that Geocontrol does not allow input larger than 4096x4096. So I was wondering if anyone knows how to make such a big heighmap still using geocontrol(or any similar tool) for realism and beauty. BTW I don't have Photoshop only Gimp, which makes me unable to just create 4x(4096x4096) and then afterwards cut them together, which I by intuition thought was the solution.

Thanks for the help in advance, I did a quick search for this but couldn't find the answer anywhere.