POVRay and Height fields and resolution...

[Crayons]

Hiya
Are there any other POVRay guys out there? Maybe the height field gurus can help?

I've been trying to generate smooth rolling hills. None of your peaky mountains for me! However, despite all my efforts I still have vertical resolution issues. I'm using a self generated 4000x4000 pixel PNG file. I've resampled it through WIlbur, softened, blurred, Gaussian bludgeoned it to death and gamma stretched it's feet off. If there were a PNG Protection Agency, I'd be up on a charge.
I still have rice paddy steps at the resolution I wanna use it at.

On the POVRay front I've taken that PNG and scaled it x2000 horizontally, and x25 vertically. I want to be able to plot things on it in POVRay using 1 meter per POVRay unit. I also want to draw on it. Roads, mud, blended into one another.

So, I have the 2 questions really.
How do I get these slopes smoother? and
How do I "paint" it - other than wacking another 4000x4000 image_map onto it? It'd be nice to be able to use map tiles (grass, dirt, and so forth) but so that they blend into each other rather than by using INTERSECTION{ } which gives me hard edges.

Heres a bit of my last render

Cheers!