Sure, those are all obstacles. But the way I see it, they can all complement each other. I.e. One of the posters mentioned drift of accuracy for some alternate

Sure, those are all obstacles. But the way I see it, they can all complement each other. I.e. One of the posters mentioned drift of accuracy for some alternate positioning methods. You could then periodically, when possible, use this more-accurate but obstacle-susceptible system to "correct" the drift.