Share your ideas people.
Hi Atom,
convert to bw, convert r g and b channels seperately and compose…
Use curves to adjust…
just some ideas,
tencars
Will something like crazy bump help to get a nice b/w heightmap? Just a loose idea.
It will be close to impossible to automatically generate a heightmap because the image has lighting and casts shadows and it has water.
The shadows will throw off the values for the heightmap.
The water will throw off the values for all ravines.
it’s only a startingpoint… 
I took a 5 min crack at it.
Use this with a displacement modifier. It would probably be much better with a higher res image.
That won’t work, the shadows and darker spots will make indentations where none should be
You’d need to repaint it or use some smarter software.
That’s why I suggested crazybump.