This is the kind of chart I adore, depicting the solar exposure of a human body at different varying degrees of azimuth and altitude. It comes from a book called Principles of Environmental Physics that I found in a free box.
Consider it a PROTIP for summertime sunburns! Don’t say I didn’t warn you.
That’s….not what I expected based on the title. Funny, though!
Azimuth and altitude here refer to sun angle, not the same as geographic altitude. Exposure to UV is much greater at high geographic altitudes, due to less atmospheric blocking/filtering. On my treks in the mountains I wear a broad-brimmed felt hat, a shirt and pants that have a good SPF rating, and put sun block on the lower part of my face. Several years ago I spent three days on a high ridge above 12,000 ft wearing a balaklava because of strong winds; forgot to apply sun block to my nose and for the rest of the week looked like I’d gotten too close to a charcoal grill.