Oh also, being able to tell how things visually change over distance is useful too. I use these less and less, but generally looking at a person at 100 meters y

Oh also, being able to tell how things visually change over distance is useful too. I use these less and less, but generally looking at a person at 100 meters you can make out a face. At 200 you can't see a face but see a head, shoulders and arms. at 300 you start to not be able to make out arms so well, and at 400 a head blends into the shape of the body. There's like a stack of different things you can use to create you're own references as well. Cities are great because generally if you can look down a long street you can see lots of things and people and start picking the differences in what you can characterize over a set of blocks.