of course not (hence the quotes), you are limited by float precision. But it can be very large.
There are other ways to create the base-terrain heights. We are working on adding it to the editor and you will be able to have a default bumpiness generated with fractals, and be able to edit the terrain with the height tools.
Sit tight for a few weeks while we work on it and then it should be good to use. We will of course make an announcement when it is ready and provide a tutorial.
Ok thanks, is there some way that I can use a float array to generate the base terrain? If I generate it from a sound fractal would it end up the same every time? Or would it generate a different fractal each time?