Our virtual earth visualizations systems free us from gravity whenever we want to take advantage. Yesterday, I was going back and forth between a site in Boston and a site in Washington, DC and some pattern recognition component of my perceptive process came alive to tell me 'you've flown that route before'. Yes, indeed, it looked so familiar to flights I made often in 1985, looking for that first job opportunity. The only difference is I was flying at a higher altitude than where commercial airlines find stable air and a manageable oxygen supply. There are an enormous number of possible navigation strategies for us to enable in exploring our virtual cities. We can choose our perspective on gravity and lighten up our emotional stance towards a rather intense phenomenon that seems to give the birds their self-esteem. Gravity as the weakest force indeed.
consider a paper on 3-d navigation