Summary

I had this printed at Shapeways in size 12 for myself, or you can print it yourself.
Please see: http://www.thingiverse.com/thing:363298 for the program that wraps height maps around a sphere. It's a Processing program, not OpenSCAD.
With these two programs together (and the ring sizer makes three) you can make any ring you want, not just the Earth.
Enjoy!
Les