Techniques to get greater levels of zoom in a iphone 3D engine?

I have a 3D globe I'm rendering using a single 2048x2048 texture (supposedly the max resolution for iphone/ipad). This limits the amount of zoom possible where at some point the 2048x2048 doesn't give 开发者_开发问答me enough resolution. Can someone point me to some LOD techniques that may be used to achieve better resolution on zoom? Thanks!

You might want to take a look at a technique called "Virtual Texturing". It is used in video games such as Rage developed by id Software to simulate very large textures.

Googling these terms should give you plenty of results such as this one: http://www.silverspaceship.com/src/svt/

Hope this helps.