Firstly, thanks for that last link - I haven't seen it for over 2 years and it's very good to be reminded of it again .. this time I've bookmarked it. I think that's where I first learned that we all lose depth perception beyond about 20 feet. That btw is why I'm puzzled re Wiley Post moving his head from side to side to judge altitude - it would make no difference, beyond that distance. (Obviously that trick is to compensate for not having 2 eyes, spatially separated)

I'm pretty sure I never move my head, as there are other ways to compensate, based on both primitive and on socially-learned levels of perception. Meaning: relative motion, where, if you're moving, distant objects appear to move more slowly across the field of vision than nearby ones .. and also, textural differences, where (for instance) distant mountains or scenery are clearly 'shaded' differently to nearby objects. That's 'primitive level' stuff, where you don't need to be familiar with, or understand, the environment, to get the depth perception.

The socially-learned level is where one simply and quickly 'gets' the spatial layout of a room or place, by recognizing the objects in it. That's the sort of perception which so threw the Apollo astronauts, who had absolutely nothing familiar on the moon which could tell them the true size of things .. even now, photos of Hadley Rille or South Massif don't seem to show how truly huge these landforms really are. We have nothing familiar with which to compare them ..

And then, there are other things like that great optical illusion which I mentioned ..

So I personally don't lack too much in every day life. I can catch a ball and piano practice is not affected (I rely on kinesthetic sense of arm-motion anyway). But sometimes I will be reminded by something disconcerting, like not being able to tell whether I'm seeing a moth close up, or a sparrow further away. At those times, it's good to be reminded of people like Wiley Post.

I also did hear about Frank Brady and really must read or buy his book. I've never flown a plane but am very into aeronautical stuff, especially those lovely older planes like that Lockheed Vega ..