I'm curious how the dark skies map is actually built. I assume it tries to make generalizations based on density of buildings. And that is only as accurate as

I'm curious how the dark skies map is actually built. I assume it tries to make generalizations based on density of buildings. And that is only as accurate as the building data is in the map source. It's probably fairly accurate overall, but there is undoubtedly some region-specific things (different lighting styles, etc) that throw a wrench into the mix. One place out my direction has a blue blob in the middle of a dark gray area, so you wonder what kind of civilization is there. Nothing, just a few buildings that are uninhabited and unlit. So there's no light pollution in actuality, but dark skies thinks there is.