I need to create a map of a region of the world, with spherical projection. I'm using Google Earth as my reference. At the zoom level I'd be using for the final product, Google doesn't offer enough detail. So I have to zoom in, but the crappy design of GE does not allow me to sync up the coordinate lines.

So given I have coordinate lines and I want to create finer resolution lines, how do I go about doing that? I cannot just take the mid point between the lines because it wouldn't be accurate especially at the steeper angles. Any thoughts?