Wednesday, August 13, 2014

Wednesday Search Challenge (8/13/14): Where can you find this in the street?

This weeks' challenge is from Regular Reader Bob Darkblue who writes: 

1.  Can you find the GPS coordinates of the manhole cover shown below?  And why does it have that odd shape?  (Neither triangular nor circular...)  

Let's make this a reasonable quest:  you don't have to find exactly this instance of a manhole cover, but just the coordinates of any manhole cover that has this particular shape.  

It reminds me of that mythical Google question, "Why are manhole covers round?"  I've certainly never used that question in an interview and don't know anyone who has.  (Besides, that's way too easy a question...)  

But I've spent the past week since Bob wrote to me with this Challenge looking around at manhole covers.  I haven't spotted anything quite like this in the streets near me, so we'll have to go looking together.  

I'm not sure if you knew or not, but I'm interested in such things. (See previous blog posts:  anode covers, SFFD cisterns, or sewers in San Francisco)  I rather enjoy the art that we can see in the world around us, even in the most unexpected places.  Here are a few of my favorites, photos I've taken in various places.  Can you figure out where they're from? 

Search on!


  1. Using information in the picture I searched [ reclaimed water manhole cover san francisco ] to
    Reuleaux triangle
    "...the Reuleaux triangle is one answer to the question "Other than a circle, what shape can a manhole cover be made so that it cannot fall down through the hole?"
    "Valve covers used in the Mission Bay Project of San Francisco to differentiate reclaimed water from potable water are in the shape of a Reuleaux triangle"

    Searched Maps for [ mission bay san francisco ] and went into street view on 3rd st. and angled my view down and found this
    Screenshot at ~1636 3rd St
    San Francisco, CA 94158

    Went back to Map view and clicked on the intersection of Gene Friend Way and 3rd St. to get

    1650 Gene Friend Way
    San Francisco, CA 94158
    37.768717, -122.389394

    1. The Reuleaux Triangle Wikipedia in other languages with gold star are very good and have more information.

      [manhole cover geometry]

      Manhole Cover Geometry

      Why Are Things Shaped the Way They Are?

  2. This is a great one! Thanks. Here's one I found.

    42.752727, -71.445206

    (in case that didn't work well, here's a link),+Nashua,+NH+03060/@42.752728,-71.445156,3a,75y,257.66h,93.48t/data=!3m4!1e1!3m2!1s8BAb3Hc3xcky_bfKQY2xbg!2e0!4m2!3m1!1s0x89e3b0e44682132b:0x4c29abd7eca40169?hl=en

  3. Hi Dan,
    This one was avery interesting one (as usual).
    The short answer:
    37.769677,-122.391091 (not exactly the one on the picture, but the same)

    First I did the naive exif exploration at but it gave nothing (as I guessed)

    Then the obvious image search lead to where I learned this was a Reuleaux Triangle shape manhole but nothing more.

    Then [Reuleaux triangle manhole cover] showed that many people were looking for that manhole and didn't find it. But in the images part I discover that your image was part of a larger one in that post: where it's said "Photo by Owen Byrne"

    So from [Owen Byrne photography] to Flickr where I search for [manhole] in ojbyrne photostream and found the original picture with no GPS data in the exif infos! But Mr Byrne had the very good idea to geotag its picture in Flickr and the Gmap showed some place near 4th street and China basin Street in SF. Went there in Gmaps street view et voilà. I'm almost sure a little more search would give the exact match (with the red painting) but I've not enough time.

    1. Excellent detective work. I hadn't realized it was from Owen Byrne.

  4. This will be brief, the website ate my original, longer description when I hit publish.

    N 37.767806, W 122.39094. The shape distinguishes between reclaimed water and potable water.

    -Saw the shape described as a curve of constant width on Mr Wizard's World many, many years ago.
    -Google search led to Wikipedia page for curves of constant width.
    -That page linked to Reuleaux Triangle as a specific example.
    -That page's Other Uses listed "Valve covers used in the Mission Bay Project of San Francisco to differentiate reclaimed water from potable water are in the shape of a Reuleaux triangle."
    -Another Google search led to the Wikipedia page for Mission Bay Project, which describe the boundaries of the district.
    -Some wandering around in Street View and I found one of the covers.

  5. Query [san francisco reclaimed water covers] Image Search

    Result Google SERP

    Reuleaux Triangle = “ San Francisco+ to differentiate reclaimed water from potable water are in the shape of a Reuleaux triangle.”

    Wikipedia “Valve covers used in the Mission Bay Project of San Francisco to differentiate reclaimed water from potable water are in the shape of a Reuleaux triangle.

    Query [san francisco reclaimed water covers reuleaux triangle] Image Search

    Result - I discovered this site as well as Twitter & Facebook were seeking the location of this image.

    Image search to Flicker and photos by Owen Bryne >click on map & obtain coordinates. 37.770799 -122.39012

    Now in Google Maps Street View we can inspect the streets & get a more precise location 37.769815,-122.389508 or 1560 E 3rd Street, Mission Bay, San Francisco.

    Shared Street View image showing several covers matching.

    1. Rosemary - a quick question if you please… in your search path description; what map are you referring to? is there a map link on the flickr site that I'm missing?
      "Image search to Flicker and photos by Owen Bryne >click on map & obtain coordinates. 37.770799 -122.39012"
      (also, if you're reading here Fred - why did you select 3rd Street in the Mission? gene friend way)
      a bit of SF history: GF
      DANGER…personhole covers
      fwiw… think "almadenmike" nailed the other covers (when I selected the Japanese cover, it IDed as Tokyo…)

    2. remmij - lucky guess. I went into street view and a couple of clicks later found them.

    3. The last manhole cover is most likely from Toyko, Japan. Why? Because when I went to download and save it the name "Cover Toyko" came up as a default name for saving the image. Not confirmed, yet.

    4. Hello Dr. Russell, Remmij, Fred and everyone.

      Remmij about your question to Rosemary, when you click on the little map in Flicker, the Google Maps URL gives you those coordinates.

      Did more SearchResearch and found:

      [Alcantarilla triangular]

      Tapas alcantarilla (manhole covers) In the comments found this link

      sewers of the World, exhibition

      [triangular manhole covers hamilton bermuda]

      Contemporary Art: Japanese Manhole Covers "...But what makes the covers so unique is that nearly 95% of the 1,780 municipalities of Japan have engraved or painted manhole covers in multiple colors and intricate designs..."

      Manhole cover. Site talks about history, shapes and other uses. Also mention manholes could be part of gps verification.

      [robotic study manholes gps]

      Future Robots Could Use Manhole Covers To Navigate Through Cities. Popular Science 2011

    5. many thanks Fred & Ramón - Fred, let me know the next time you visit Las Vegas;) - thanks for the prompt Ramón - I wasn't aware of how that worked.
      I kept looking for a little map icon instead of clicking on the photo location… doh - handy piece of info inching forward
      ojbyrne map

    6. Ramón - following your lead, found this from the foundry site (on flickr) - I was having a hard time locating this cover…

    7. Ramón - wanted to point out that the Japan cover photo wasn't the same photo, but the same cover pattern - so the pic Dan used is still running loose in the wild…
      the China Basin covers you & Mr. Warden discussed, excellent sleuth work by Mr. Warden —
      great example of social/crowd sourcing info very cool Owen Byrne responded… and remembered the location!
      btw, Fred - even if it's Atlantic City… maybe we can get this "lucky" guy to join us…

    8. Good thing I copied because I now have the disappearing bug. Interesting.

      Remmij - I did respond to you but I see Ramón helped you out. If you don't see a reply to any question you ask me something has happened because I will always respond. I don't know what happened because my other posts all seem here but I'm going from memory. Normally I save a copy in Google Docs but with a quick answer I forgot to copy.

      Here's a collection of manhole cover locations saved in Google Maps. Dr. Dan have you done such a map. I didn't find one. I had searched ¨mapping manhole covers¨.

      I don't know if anyone has an app that reads foreign language signs. I have the free version of Word Lens & I was going to try to read the japanese writing on the cover but my free version doesn't have japanese.

      I will never look a manhole covers quite the same way after this challenge. Thanks again for opening my eyes to something I would not have noticed. My world just got a little bigger. And yes I copied this post just in case.

    9. Based on the reference to “why are manholes round” you may enjoy this book known by that name. Mind you it may not be Google material as you’ll see. And others find manhole covers just as interesting

    10. Thanks, Remmij for your posts.

      Rosemary, did you try with Google Googles or Google translate with image as we did in What does this character mean?

      Then tried Tokyo manhole cover photo after seeing Remmij post. image with [Tokyo manhole cover ]
      drainspotting: 61 amazing manhole covers from Japan.

      Finally, I was practicing this morning with Dr. Russell's earthquake video and searching found this
      Dr Daniel Russell - Teaching 150K+ Students at a Time. In The University of Edinburgh 2013.

    11. Yes Ramón I did but my drawing was so pathetic it didn't come close to any japanese symbol. I actually questioned whether these were japanese symbols once I began drawing them. Using a touchpad isn't ideal. Anyone got a touch pen would have much greater success.
      I also tried guessing the words

      1 recycled water

      2 reclaimed water

      3 sewer

      4 Tokyo

      5 storm

      1 再生水

      2 再生水

      3 下水道

      4 東京

      5 嵐

      Nothing worked. Any guesses?

      I was trying to link the Drainspotting as well but it didn't work. Glad you did Ramón.

    12. So many comments! Nice.

      In brief:

      Ramón's trick of getting the geocode of a Flickr photo is a good one to know. Many Flickr photos have geocode even in the absence of EXIF data.

      Also, thanks for the link to my Edinburgh talk. I guess I'd forgotten to point this out to the blog. (Too many talks, too little time!)

      Rosemary - Did you try to sketch the characters using ShapeCatcher? (I assume so, but just checking.) Yes, a graphics table would be a huge help.

    13. And no, I haven't done a Google Map for manhole covers. That's a great idea, though!

    14. Rosemary, appreciate the heads up (1:43 PM)… the "disappearing bug" is curious - really seems to be bedeviling Vancouver Jon tU. You made DrD's day with your expanded world view comment.My favorite cover
      this was an interesting challenge - thanks to Owen Byrne for the ▲ impetus. back to ☕

    15. …like a Rolling… uhh, Manhole Cover…
      Bob Dylan, Duluth

  6. Here's what I found:

    Searching [triangle manhole cover] ...

    The trianglish shape is a Reuleaux triangle. From the wikipedia entry (( "It's a curve of constant width, meaning that the separation of two parallel lines tangent to the curve is independent of their orientation. Because all diameters are the same, the Reuleaux triangle is one answer to the question "Other than a circle, what shape can a manhole cover be made so that it cannot fall down through the hole?" The term derives from Franz Reuleaux, a 19th-century German engineer who did pioneering work on ways that machines translate one type of motion into another ..."

    Searching ["san francisco" reclaimed water" "manhole cover"] led me to a series of sites that showed your first photo ... and its earlier uses.

    This image has a history dating back to Aug 23, 2006, when Owen Byrne says he took it:

    Mathematics Association of America "Found Math" Week 21 featured it:

    As did the organization's MAA Focus magazine (Jan 2009 p22 ... )

    This summer, math writer Ivars Peterson was in residence at the Exploratorium and asked for help in finding its specific location:

    While commenters didn't give any specific locations for it, David Wills did post a photo and location of a similarly shaped one in Sonoma:

    383-397 1st St W
    Sonoma, CA 95476

    The Google Maps view ( doesn't seem to have the resolution to see the cover itself, but here are the coordinates for the intersection: 38.293810, -122.458613 ... which should come close to satisfying your request for "coordinates of any manhole cover that has this particular shape."

    As for the four pictured covers:

    1) Google/Mountain View (
    2) Disney World (many web photos of it)
    3) Rome (searching on the text gives: )
    4) Japan (from writing on the top). While I didn't find this specific cover, I found (Google Image searches like "manhole cover" Japan]) an incredible number of photos of gorgeous Japanese manhole covers on the web.

    I wish I had more time today to track down more specifics. But what a revelation that they are so many lovely manhole cover designs. While there are obviously many who appreciate them, I wonder who are the folks who commission and design these functional works of art rather than settling for the mundane.

    Best wishes,

    -- Mike

  7. I started by looking at the text on the photo to find search terms.
    My first search was 'reclaimed water manhole sfwd'
    The top result was this Wikimedia Commons image -
    Apparently it's not used on English Wikipedia, but this Ukrainian page has it -
    Using Chrome's translate function told me it's a 'Reuleaux Triangle'.
    The 'Covers for manholes' section of the page mentioned San Francisco's water recovery systems hatches, and that 'with a constant width, they can not fall into the hatch'. This is where the photo is used.
    Now I had a more specific term, I looked up 'reuleaux triangle san francisco'.
    The first result was and the snippet mentioned San Francisco, so I went to the page and did a find for "Francisco".
    This told me "Valve covers used in the Mission Bay Project of San Francisco to differentiate reclaimed water from potable water are in the shape of a Reuleaux triangle".
    I followed the cited page at but it didn't tell me anything new.
    I now had a more specific location, so I searched for 'mission bay project san francisco'
    That only led to generic development plans, so I made it more specific as 'mission bay project san francisco reclaimed water'
    The top result was , and I know San Francisco well enough to know that Mission Bay is on the east side of town, so it's likely to be the same project.
    The page is mostly a technical description of the project, but does include the summary "will provide recycled water to customers located predominantly in the Mission Bay".
    I went back and looked at the challenge, and realized it was to find the GPS coordinates of the manhole. The image is identical to the MAA found math page's one, just cropped and rotated.
    I used Jeffrey's Exif Viewer on both the blog post image and the original I found, but there were no GPS coordinates embedded, e.g.
    I then used "Search Google for this image" in Chrome to find other instances of it, and came across
    This was interesting, because it was the same photo and challenge. If I could find the answer other people gave, I'd have the answer myself.
    I looked through but no answers were mentioned.
    I then looked through, but still there were no results.
    I went back and did a search for 'exploratorium reuleaux manhole', and found a Facebook discussion page as the second result -
    There was lots of discussion, but no conclusions in the comments.
    I then took a step back and searched for 'reuleaux manhole san francisco', and found a page on Flickr that appeared to be the original source of the photo, taken by Owen Byrne.
    Going to his personal site at he's an interesting guy, the original programmer behind Digg. I found his Twitter account, and sent him a message asking where it was taken. He replied quickly with "Not completely sure, but I think 3rd Street in Dogpatch"!
    I then re-read the challenge for a third time, and realized it was for any cover that looks similar, but I'm happy I got a lead to the original source at least!

    1. Hello Peter, I just read your post and Mr. Byrne answered you again:

      "@petewarden Actually one of the comments refreshed my memory. 4th and China Basin in Mission Bay

      Mr. Byrne address in Google Maps

    2. That's a superb answer, Pete. Thanks for all your work on this. Impressive!

  8. Good day, Dr. Russell, fellow SearchResearchers


    Search Google for this image.

    Reuleaux triangles there link sends to Reuleaux triangle Wikipedia

    [reclaimed water]

    [triangular manholes covers san francisco]

    [mission bay san francisco reuleaux manhole]

    [reuleaux owen byrne]

    Owen Byrne photo with map

    To find the other manhole location.

    Image with [Google manhole]. It is located in Googleplex
    Image with [Mickey Mouse manhole] It is in Florida
    Image with [Servizio dei vigili manhole] and [spqr 1966 manhole] It is in Rome
    [concentric circles manhole] Images with beautiful manholes.
    [Japan manhole circles] Images with beautiful manholes.

    I was going to crop and search image and found that images from covers have their name on them.


    1. Can you find the GPS coordinates of the manhole cover shown below? And why does it have that odd shape? (Neither triangular nor circular...)

    A. Mission Bay San Francisco

  9. PUBLISH failed yet again

    noticed the 'RECLAIM' cast into it

    SEARCH [elliptical triangle manhole cover] which lead to

    where I learn its name is REULEAUX triangle which has constant width. A link to

    Valve covers used in the Mission Bay Project of San Francisco to differentiate reclaimed water from potable water are in the shape of a Reuleaux triangle

    SEARCH [reclaimed water valve covers san francisco] leads to emergency water in several places

    "In order to extend the Aúxillary Water Supply Ssystem protection to outlying parts of San Francisco, the Department of Public Works is cooperating with the San Francisco Fire Department to build a dual-use fire protection/reclaimed water (RCW) system"

    Where is this #Reuleaux #triangle manhole cover in #SanFrancisco? Help us & our Osher Fellow @mathtourist find it!

    Also Where is this #Reuleaux #triangle manhole cover in #SanFrancisco? Help us & our Osher Fellow @mathtourist find it!

    The Exploratorium also asked this question but I see no one got it.

    Well after some searching I hit upon this strategy; I went to the maker D&L Foundry and found there at

    I find our item in their catalog as M-9009 or M-9019 Valve Box and the GPS co ordinates via EARTH for the foundry are

    47.132479 -119.216738

    I know; its a cheat but I had to find something tell us that the High Pressure System is also called Auxiliary Water Supply System

    There is a nifty hand drawn map of the High Pressure System here

    High Pressure hydrant locations map

    I surrender.


  10. I'm sorry but… my eyebrow went up when I imagined the SE analysts at Google scratching their heads over the spike in the search term [beautiful manholes]
    especially as it went through multiple iterations and translations and filters…
    Brooklyn represents
    flat rainbow
    the 0 would make a fine cover
    have a fine friday everybody ;)
    tiny devilish