I believe I described it badly or you misunderstood me then. What I was referring to in my mention of three-dimensionality is that the area in which all of them orbit isn't a single flat plane over a sphere shape. It's actually several flat planes layered on top of each other, with an obviously ever greater surface area the higher you go. Thus you have LEO, MEO and GEO satellites all sharing orbital space but at different heights so to speak. I'm aware that any given satellite generally flies along a fixed altitude (though as far as I know their latitude along that altitude can shift enormously)