Set Texture on only particular part (portion) of a Sphere

Hello Everyone,

I am using Unity 3 Version 3.4.0f4.
I am very new to Unity3D and also 3D concept.
But I am good at programming with C#(.net). I am creating application same as Google Earth in Unity3D with C# scripting.

I have taken one Sphere and give a simple World Map Image as texture to it. I have also written script in C# for Rotation and Zooming the Sphere like Google Earth.

Initially up to some Zoom-In level I want to keep the same Texture. When Sphere will Zoom-In after some level at that time I want to change the texture which can display more detail view of earth location. This things will be repeated up to last Zoom-In level.

I am getting Longitude and Latitude value of Sphere on Mouse Over and Double Click event.

For that I want to set Image of specific part of World Map on the Some Specific Portion of Sphere only. Like wise using C# scripting I want to change images as per users iterations with Sphere.

Can anybody suggest me how can I accomplish this thing.
Since long time I am trying to do this thing.
If anybody can give sample code then it will be better.

Thanks in Advance.

You can mess with the UV’s on the sphere mesh. At some point as you zoom in, though, you’ll want to discard the sphere and use flat (or flatter) meshes because for something the size of Earth, floats won’t cut it at extreme zooms.