What is the best way in making massive terrain? Not the infinite tiled terrain. I only use the infinite for the ocean part. I'm working on a simple hybrid type RST/FPS war simulation game where in I'll be having aircraft like jets that can fly fast.
My plan was to make 2 massive island and few small once separated by the ocean making it more massive. But still making transportation possible with aircraft.

My current test map's size is just a quarter of my target total land size. It uses a 128x128 hmap and colormap. Imported in med 65535x65535 terrain size, 183x183 face size, scaled to 50x50x40. Problem with this is when I'm in a ground unit the terrain polygon shakes allot. I have set my camera clip far to 130000*5 allowing me to see big part of the map while in aircraft mode. Having large view range will load more of the terrain's triangle and I don't want to use up my polygon count on the terrain alone. I already plane my map to be a desert type map, that way I don't have to think much about terrain entity and will concentrate more one the code it self.

I was hoping to make multiple tiled terrain but don't have no idea where to start. Specially from making several terrains that will tile nicely. And does 3DGS have a terrain LOD feature that will reduce terrain face at far from without cutting off faces from my current position?