I left the autumn discussion on Wayfinding unresolved as to whether full overhead mapping was at all hardwired or merely a recent variant of sense of direction (as opposed to landmark navigation.) I had felt strongly there must be something of a heritable spatial ability, but the evidence for it was elusive. Dead reckoning seemed to have more experimental evidence behind it. Jennings makes several references in Maphead to navigating as if from above eye level, but not looking down at a flat 90 degrees as on a map.
Something between 10 and 30 degrees seems to come automatically to some folks when picturing medium-distance navigation, rather like an actual bird’s-eye view, elevated but looking forward, rather than what we usually call a bird’s-eye view. I don’t know of any research on it, but it seems likely. It would be the view one would have from a mountain or rise of land, or even from climbing a tree. Extrapolating that to picturing an area in one’s head, even things which could not actually be seen from any earthly point, seems entirely plausible. A slight angle of elevation would be more closely related to dead reckoning and compass orientation, but once the concept of getting off the ground was in place, once that seal was broken, exagerrating it to full 90 degree overhead doesn’t seem so odd.