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Discussion Starter · #1 ·
Saw a few of these on the roof of some buildings in SF. They were all pointing in basically the same direction, but no idea what they are for. Ideas?
 

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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...
 

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Probably optical beam detectors to sound a siren to keep kids off the roof, put your hand in-front of it and see if it trips a buzzer. :laughing:
 

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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.
 

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Good grief

What a puzzler! I haven't a clue (although I like the pigeon-zapping idea).

As someone else asked, is that a reflector in its center?
 

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Discussion Starter · #11 · (Edited)
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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