Railworks America

I'm making a route using STRM data and I imported data by a 19X19 base and I have came to the limit, what do I do to keep going with terrain without affecting my previous terrain I imported before which happened to me and I don't want to happen again. Do I use a different size or use the same? Or what else, etc?

Keep importing away. If your next 19x19 set of tiles overlaps the first, it won't make any difference.

Now if you have modified (raised, lowered, etc...) any terrain, and import over it, the modifications you had made would be erased. If you have just started your route, I would suggest importing most of the terrain along the path of your route at first. You can always fill in terrain on the periphery later.

Also, you only need to establish tiles of terrain that you will see from the train or if distant terrain has those square edges you can see from the track location. That last part would mostly be a problem with terrain that has raised areas like mountains and hills. Just establish all your tiles needed from the track location and adjust from there before you do any track laying. Having the large grid turned on when doing this helps you see how the tiles are laid out.