Re: When to use createWorldToLocal of osgEarth::GeoPoint?
Throughout osgEarth, the term "world" refers to the actual XYZ coordinate system used for rendering. For a round-earth map, the world coordinate system is ECEF. (For a projected map, world coordinates are the same as map coordinates.)
The createWorldToLocal function creates a matrix that transforms a point from World coordinates into a local tangent plane centered on the GeoPoint.