[aptpupil]

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?

 

[EmmCeeDee]

Is that a reflector in the center? Are they visible from the street?

 

[Tinstaafl]

Focusing lenses for laser pigeon-zappers. :thumbsup:

 

[hdavis]

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...

 

[Inner10]

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:

 

[pritch]

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.

 

[griz]

Anemometer?

 

[EmmCeeDee]

Something for the fire department?

 

[rosethornva]

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?

 

[Calidecks]

Its an Antidisestablishmentarianism device

 

[aptpupil]

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.

 

[m1911]

I think they use them for surveying

 

[Calidecks]

I think they use them for surveying

I think this might be a good answer.

Possibly shooting elevations

 

[EmmCeeDee]

That would make sense. They could be used to triangulate. Are they oriented toward the new building?

 

[hdavis]

Maybe one of these:

https://www.google.com/search?q=min...J46WyATbwoJg&ved=0CAkQ_AUoAg&biw=1366&bih=657

 

[Robie]

I think they use them for surveying

http://www.berntsen.com/Surveying/Survey-Prisms/Mini-Prisms

 

[TimelessQuality]

http://www.berntsen.com/Surveying/Survey-Prisms/Mini-Prisms

For earthquake detection/monitoring?

 

[aptpupil]

That would make sense. They could be used to triangulate. Are they oriented toward the new building?

Not exactly, but in that general direction.
Thanks guys.

 

[hdavis]

Crap - I forgot to take off my cloak of invisibility before posting:laughing:

 

[Calidecks]

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