[cousin_it]

Agreed. You could slightly improve the naive implementation by restricting the north-south rotation so you can't go beyond either pole, so north always stays up. It's not just for the Earth either, I'm now working on a 3D object editor and decided on the naive implementation there as well, because when you're sculpting a chair, it's annoying if up doesn't stay up.

[BitMastro]

Please do, when I used some 3D editors with that behaviour I was going crazy.. Then I had to remember to restrict the rotation using a modifier or a button.

I don't know where I've seen this, but I think dragging an arc drawn outside the object to adjust the roll is the best solution to the problem.