The above pg implements controls that are similar to most mapping solutions (panning keeps mouse in same position, as does zooming), and is basically a stripped down version of the control system I used here (though there the camera was also heavily modified so as to allow both rotation around the globe and about the surface target. The 2d mode available through the tools menu could have been done using the control scene from the pg and the standard camera however. Touch controls are also implemented there but not in the above pg). There may be a more idiomatic way of implementing custom controls though.
I'm not sure if this is entirely what you're looking for (2d plane navigation), though I think it could be extended to work in 3d zooming in to a plane parallel to the viewport. Let me know if anything in there is unclear.