The two low res images total 60Mb, the main canyon is 475Mb, going as far west as Vulcan's Throne. 1Gb RAM to load, another to render. I relocated them to the top of the planet.
I made another image for the area west of that but that's another 410Mb (they're 32bit, LZW compressed). I may have to be a little more methodical and split it up into more manageable squares which would also let me crop a little closer to the canyon edge. That would also let you use less high res data if you're only interested in a specific area.
It is very nice being able to simply load higher res terrains on top of the others without having to mask. Must dig out a global DEM model with bathymetry to see if it's practical to do the full outer space to surface animation.
[edit] Had a quick play, pulling down a 0.05° global geotiff (105Mb) and the 2 higher resolution images. Had to remove the outer image from the set as it had gaps at the edges. Should be able to share the data as it will now be a mixture of multiple (public) data sources. Definitely needs the intermediate terrain to improve the transition around the main terrain but it's looking pretty good. Blue surface just altitude limited to 1m, but I'd use an ocean mask to exclude Death Valley and other low lying areas.
Also had to turn off ray tracing objects for the high altitude render to avoid black patches.[/edit]
