In Geoscape if you click 'Edit Texture Settings' then click options tab, then change output texture size from 256x256 to something like 1024x1024 or even 2048x2048.
Now Geoscape has a detail textturing button. I'd turn this off so your Geoscape texture looks like it would in Dark Basic. Dark Basic Pro does have 'Detail Texturing' but it doesn't work
.
What I now do is open texture in Paint Shop Pro and do a bit of work making texture more detailed.
One final thing, when using Geoscape I always export as a .x mesh which trebles my FPS.
The word "Gullible" cannot be found in any English Dictionary.