What are the mysterious light sources on light pollution maps?
Ah yeah, in the post's first "unknown light pollution" example, I figured it must be a greenhouse.  I was driving through a relatively small town one time and was a bit freaked out by this ominous yellow glow off in the distance.  Like, the whole sky was glowing [0].  I ended up driving out to try to find the source, and discovered it was a huge greenhouse/farm.  Luckily not an extraterrestrial landing zone or so on ;)[0] looked like this https://i.cbc.ca/1.4925044.1543460834!/fileImage/httpImage/i...