My guess is reflectors for a laser, but who knows why. If you wanted to monitor ground movement in a city, you'd really have to just put the laser reflectors on roof tops, but that only gets you position in one direction...
No clue, really, but it certainly don't look like it's held down very well. It almost looks like a gob of something oozing out from the edges of the mount, but I can't really see any kind of fasteners. At any rate, I'd hate to have the fool thing land on me.
No moving parts. No circuitry or anything like that so I don't think it's measuring anything.
Like I said, there were several of them. Two on the rooftop I was on and a few more on buildings nearby. All adhered with silicone or something similar. Not visible from the street. There is a building going up 100' away or so, not sure if that has anything to do with it, though. Construction just started.
They all point in the same direction. They have a reflector and crosshair type thing inside.
My best guess is it has to do with surveying in some way.
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