Spherical mapping create UVs using a projection that is based on a spherical shape wrapped around the mesh. This projection is best for shapes which can be completely enclosed and visible within a sphere, without projecting or hollow parts.
To create UVs using a spherical mapping technique
Projection mapping only works properly on a single object at a time. If you need to apply a projection to multiple polygonal objects in a single step, combine the objects into one, apply the projection, and then separate the parts back out. Otherwise, perform a projection on each object separately.