Hi Jim,
Question 1:
At the moment L3DT doesn't have much of a facility to post-process heightfields after the initial generation. What will work, to a degree, is to re-size the heightfield to something smaller (using operations->heightfield->resample map), and then to re-size again back to the original. The effect of this will be to do a linear blur of the map, but it wont affect the locations of coastlines &c.
Here is an example of a before and after sequence, where I've taken the heightfield down to 1/4 the size, then brought it back up again:
Before:
After:
You can see that most of the high-res noise is gone.
Question 2:
By alpha layers are you referring to the 'operation->alpha maps->generate maps' option? If so, I have a brief rundown of
alpha maps here, a more fulsome discussion of their meaning and use
here, and a user-guide on generating them
over here. Basically, they are mask images used to create textures for objects 'on the fly' from a set of base textures. It's a trick commonly used in games these days. If, however, you meant something else by Alpha Layers, could you give me an idea of where you're looking?
Cheers,
Aaron.