How do I tile a sphere ?

Hello,
    Thanks for reading.
In the past I have received help from you guys on this NG and am hoping
once 
again you could be so kind.
I've been working on a 3D Earth type program using OpenGL with GLUT.
Currently I load a rather large single texture of the earth and cover the 
sphere with it, this works OK but is a bit slow at loading.
I think I need to convert to a tiles approach where I divide the sphere
into 
say 512x512 tiles then texture each tile individually to speed things up a

little and make future zooming in easier.
I could then of course load/cache each tile on demand when its within
view.
These ideas are nothing new I know but I could really do with a small 
skeleton tutorial or whatever on how to do this so if you know of one I'd 
really appreciate it.
I have Googled around a bit and found stuff talking of "Quad Tiles" etc
but 
no decent example code.

Thanks in advance

Lynton, England UK

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