What is this thing mounted on a San Francisco building?

We are having fun in the G+ Boing Boing community. Our friend Rob Walker posted this photo and said:

I was in San Francisco recently and walking from Market/8th to the SF CalTrain station I kept noticing these odd little things, mounted about 10 feet off street level, a few-inches-wide tire-like object often (but not always) accompanied by small target symbols. What is it, is it functional, or some sort of street art thing. Anybody know?

Mark Frauenfelder is the founder of Boing Boing and the editor-in-chief of MAKE and Cool Tools. Twitter: @frauenfelder. Come and hear Mark speak at the ALA conference in Chicago on July 1.

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http://upyernoz.blogspot.com/ upyernoz

we have something that looks like that in back of our 120 year old house. i always assumed it was for tying up a horse.
- http://daruiburns.tumblr.com/ Dlo Burns
  
  That high up?
  - beemoh
    
    Maybe this particular household preferred to ride giraffes?
http://twitter.com/TimmoWarner Timmo Warner

Not knowing anything about it at all, my guess is it’s for measuring if buildings are moving/shifting after earthquakes.
- euansmith
  
  Given the location, that was my guess.
- Paul Renault
  
  I’d say that’s a good guess: It might be one of these.
  http://www.surveyequipment.com/surveying-accessories/prisms/cmp104-monitoring-mini-prism-target-with-l-bar?zenid=2tv0h2f0vtobd6fqe2748fq394
  
  They could use them to tell if/when the buildings have moved.
  - Christopher Scollo
    
    I see these around central London too. They’re in place to ensure the buildings are not undermined by the work being done on the new Crossrail railway line.
- logicslayer
  
  That was the first thing that popped into my head.
Terry Carroll

I believe that’s an anchor for formerly pole-carried utilities, now under-gounded. I don’t recognize the “target,” but my bet is that they are patches over the former holes where the lines, from the anchor, entered the building (and they merely look like targets).
missamo80

The two targets are surveyor’s targets. Since the building is highly unlikely to move it gives a fixed known location that can be used in distance measurements and whatnot.

Here’s a random page I found with some searching that shows them: http://www.surveyequipment.com/surveying-accessories/reflective-targets.

The round red thingy is probably also related to surveying/construction.
- ujin
  
  Yea, there are two paper targets which are useful for most surveying but are not as high precision as some operations require. The larger red looking one is a survey prism which is typically used when the accuracy/precision demands of an operation are high or you are gathering lots of data over a long period of time.
  - soap
    
    Those adhesive targets are likely plastic, not paper. The bottom one appears to be Trimble brand (based on the crosshair design.)
    
    The need for a prism for accurate EDM is outdated, my LiDAR scanner can get sub 3mm accuracy w/o a reflective target, and my total station can do darn near 1mm ranging on anything – prism or paper. The only reason to use a prism with modern equipment is if you’re going fully robotic target acquisition. Though they may be using the “red” target simply for off-axis aquisition. Those flat targets are only really appropriate for use when your line of sight is perpendicular to them – use them from a side angle and the width of your EDM’s spot becomes a factor as you’ll get returns from multiple distances.
    
    EDIT: Though I swear I can see the word “Leica” on the top targer. Odd in that Leica and Trimble equipment are rarely seen to mix in the wild.
http://www.alannacoca.com Alanna Coca

I’m pretty sure that’s one of those things the aliens put on our buildings to help them scale the walls. The targets are actually reminders that there was no intelligent life found within.
ultragreen

It’s definitely some kind of alien technology.
http://twitter.com/digitalArtform Joseph Francis

It’s a receiver for a laser communications beam.
http://www.facebook.com/profile.php?id=597218474 Taylor Flannagan

It’s people.
- euansmith
  
  No, you fool, that’s Soylent Green
Philboyd Studge

It’s a Portal toilet seat.
- euansmith
  
  I love the name, you Saki person :D
- Donald Petersen
  
  Your business is appreciated.
foobar

Here’s one theory: http://www.viruscomix.com/page567.html
- Kenmrph
  
  just read it… loved it!
- http://www.facebook.com/people/Rick-Adams/100000053021803 Rick Adams
  
  It’s a beautiful and entertaining read, but being a contractor used to working under the table, none of those examples looked like anomalies to me. And the “node” in the comic that looks like the picture above is certainly a piece of leftover knob-and-tube wiring. More specifically, the knob.
- http://asterozoa.tumblr.com/ Kat
  
  I was about to link to this same comic! Awesome, foobar.
- euansmith
  
  Thank you for the link. That was a nice diversion.
- daneyul
  
  Loved that! Thanks for linking to it!
Alyx McCown

looks like a retro reflector to me … probably for statistics getting of land movment … look directly across it for some sort of laser box
- TNGMug
  
  Almost right! The laser box will be a surveyor’s transit (or “total station”). So it won’t be operating continuously. More likely they’ll just show up every week or so and take a single measurement. What you can look for, if you’re that interested, is reference points drawn on the sidewalk, or nails driven into the street, and labeled in spray paint with some kind of number. These will be their reference points for where they will set up their tripods.
http://www.facebook.com/people/Rick-Adams/100000053021803 Rick Adams

If you put that on the staff while the sun is setting at Equinox, it opens the well of souls.
bobcorrigan

Hobo map waypoint markers.
pjcamp

If it were Charleston, I’d say earthquake bolt. Being San Francisco, I’m betting something to do with weed or condoms.
salo

As per the Hotel Utah in the background, this appears to be on 4th street where the new central subway line in being built. I wouldn’t be surprised if they are concerned about buildings moving as they dig the new tunnels.
- TNGMug
  
  I would nearly guarantee that’s spot on. I have personally put these things up on buildings near new condo developments in a city where earthquakes are pretty much completely unheard of.
- http://www.facebook.com/roland.turner Roland Turner
  
  This is my guess; I’ve spotted dozens of these on older buildings in Singapore near excavation work for new MRT (underground railway) lines. Presumably getting early information about subsidence – and/or confirmation of it not happening – are pretty important when tunnelling near/under old buildings.
professor

It’s infra-red magnifying glass death-ray for Bullet Ants. Bullet Ants are naturally drawn to a bulls-eye target, and once centered the magnifying glass cooks their asses (while giggling in a particularly childish manner!)
limeychiney

Perhaps for some kind of self-driving car guidance system?
voiceinthedistance

Ground based gaydar installations. San Francisco uses theirs with the polarity reversed, to detect straights.
http://twitter.com/stuck411 David

I know they use the same tech on buildings that they’re afraid are moving/might move. The guy mentioning the tunneling nearby probably nailed the answer.
tw1515tw

We left mirrors on the moon, and I reckon someone has left the equivalent on Earth.
http://artdonovan.typepad.com Art

It’s a dog toy. Some kind of new “Kong”- for very tall dogs.
You put the tasty treat in the center.
http://pulse.yahoo.com/_GVKHNINUD55NXFN4TRNHMBRDB4 Alexandros

May be an ancor for the overheadline of a former street car line? You find tons of those on old buildings here in Frankfurt. They look different thou.
TNGMug

Those are most indeed survey targets. I know because I’ve had to install survey targets myself, and for the purpose of detecting building movement. I do not however live in San Francisco, the city I live in is well out of an earthquake zone.

At 10 feet those are for a lower reference point. Look very carefully way up on the building, they should have installed a second set at the 7th-ish floor or so.

Look around the area. Are there any new developments within a block or so? If so, if anybody is driving piles or shoring beams, then a monitoring program of the surrounding area will be warranted. Even small shifts if the soil can mean big issues, especially in buildings that old.

Of course this is San Francisco you’re talking about, it could be for fault movement, but just to say, these kind of monitors are hardly restricted to that kind of program.

[Edit- Above poster mentioned a new subway tunnel is being dug in the area, I can nearly guarantee that's exactly what it is, and that said tunnel contractor received the invoice for the installation and monitoring of these things via laser total station]
Dexter Sinistre

It’s a nose ring (using Feng-shui, that’s where the building’s nose is). The markings are tattoos.
KWillets

All the buildings in that area are basically floating on mud. Monitoring movement is fairly common.
hungryjoe

Navigation waypoints for drones. Obviously.
http://www.facebook.com/ted.leaf Tim Leath

aliens