Geohashing

Posted byRandall 246 Comments on Geohashing

Almost four years ago, I posted a comic laying out the Geohashing algorithm. The algorithm generated a set of random latitudes and longitudes each day, spread out across the globe so there was generally always one within a few dozen miles of every location. I figured they could be used for hiking destinations, sightseeing, meetups, or whatever else people came up with.

I wanted to make an algorithm that anyone could implement, which didn’t rely on a central authority or ongoing support from any one maintainer. I also wanted to make it impossible to know the locations more than a day or so in advance, so that if geohashing became popular in an area, no one could publish a list of future locations that woud give property owners, park rangers, or local police time to prepare. So each day’s coordinates are randomized using the most recent Dow Jones opening price, which isn’t known until the morning of that day—or, in the case of weekends, a day or two in advance, which helps with planning larger weekend trips.

In the days after I posted the comic, there was a flurry of geohashing activity, which quieted down as the initial novelty wore off. But it didn’t die, and for the past several years there’s been a small but vibrant community building around the Geohashing Wiki. There are numerous daily expeditions, and they’ve taken some beautiful pictures and come up with a lot of neat tools, games, and achievements.

One of the many things they did was use a tweaked version of the algorithm to come up with a globalhash, a single coordinate for the day somewhere on the planet (biased toward the areas near the poles). They’re usually over the ocean, but a few of the land ones have been reached.

Yesterday’s globalhash fell less than a kilometer from the South Pole. User Carl-Johan got in touch with the Scott-Amundsen research station, and later that day, the hash was reached by Katie Hess, Dale Mole, and Joselyn Fenstermacher of the US, Robert Schwarz of Germany, and Sven Lidström of Sweden.

Wow. Just wow. Congratulations.

If you want to look up today’s geohash for your location, you can use this online tool, or one of the others listed on the Coordinate Calculators page.

246 replies on “Geohashing”

  4. You have excellent posts in your blog. But why do you use WordPress default theme for your site? And event dont have any about, policy, contact page?

    Thank for your post!

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  6. GEOLOGIE.
    There are thousands of us reading about mining children for organs with
    RRAPOP.
    And it’s the ZETAS 99 who are letting this information out for deals.
    Who knew the QUEEN was ” GREED ARK”?
    Who knew she worked in international mob?
    BUSH- CHENEY- CLINTON- ROVE- CONDOLEEZA RICE.
    GEOHASHING?
    This is that ROCUNROL with UNITED NATIONS and ” DWYT” – 169.
    And they are involved with HOLLYWOOD – EDWARD MEESE- to SLYMIC.
    DESASSOOSSEGOS – DASSAULT- NYSSE.

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  7. First time I tried this, and I landed almost in the Dutch Royal Palace. I can ring the door, but I highly doubt the queen will invite me in for coffee.

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  8. Is there a distribution plot available to show the random (or biased) nature of the globalhash? I have this nagging feeling there are areas within any given quadrant that will never be selected for a globalhash, is this correct?

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  9. nm previous question, i was not paying enough attention. back to waiting patiently for the ultimate couch potato achievement.

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  11. For Phoenix area your boxes are too big and too far apart. Consider an overlaid grid where you double the density by putting new boxes at the intersections of old boxes. This will allow many more people to participate.

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  14. Pingback: » Now there’s a neat idea Some Blithering Idiot

  20. Ben vous l’avez et en couleurs en plus M’sieur le juge ! Délaissez un peu le Code Civil pour une chambre photographique et prenez des soldats en train de poser ainsi (si vous en voyez s’écrouler ainsi sur les bancs de la capitale, ça fera un beau cliché !). A moins de détenir une carte de presse (et encore !), vous devriez avoir toutes les peines du monde

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  21. On peut cependant voir quelques voitures sur certains clichés…
    En fait la majorité des autochromes présentés sont datés de entre 1920 et 1928. Certes le trafic n’avait rien à voir alors avec celui que nous connaissons. Mais quand même, je me dis que l’absence totale de voitures sur la majorité des clichés est un peu étrange pour l’époque (et probablement volontaire).
    J’ai également remarqué que le revêtement des rues paraît lisse. On est plus sur les gros pavés dont s’accommodaient chevaux et fiacres. Sans doute déjà du « macadam » ?

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  22. Si ça peut vous rassurer, comme le précise le papiel (papier électronique ndlr) en lieu et place de capteurs numériques, c’est de la fécule de pomme de terre qui servait d’émulsion, en partie bio-dégradable donc !

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  23. L’auteur de ces photos russes, Sergei Mikhailovich Prokudin-Gorskii (1863-1944), utilisait une autre technique (aux meilleurs rendus à mon avis): « Chaque photographie est en fait le résultat de trois clichés pris très rapidement. Chacun était en noir et blanc mais prises avec des filtres rouge, vert et bleu. Les trois prises de vues pouvaient alors être recombinées et les couleurs étaient très proches de la réalité. ….

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  24. Je trouve cela limite malhonnête de ne pas citer la source de ces photos: les archives du Musée Albert Kahn. Le blogueur de Paris 1914 explique que les photos viennent de cette collection extraordinaire mais vous n’en parlez pas dans cet article comme s’il avait trouvé ces photos dans sa cave… Ce n’est pas très sérieux.

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  25. Les autochromes n’étaient pas si rares au début du siècle et on en voit fréquemment dans des expositions de photographie historiques (par exemple actuellement au Musée d’Orsay, celle sur Félix Thiollier).
    Le musée Albert Kahn est loin d’être le seul à avoir de telles collections, il y a aussi Orsay, la SFP ,…

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  26. Les photographies d’enseignes au néon, sont, je e crois, de Léon Gimpel, qui fut exposé à Orsay début 2008.
    Enfin, je ne suis pas un expert en technique, mais il me semble que beaucoup des photographies sur le site que vous mentionnez ont été (parfois lourdement) recolorisées.

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  27. Les autochromes n’étaient pas si rares au début du siècle et on en voit fréquemment dans des expositions de photographie historiques (par exemple actuellement au Musée d’Orsay, celle sur Félix Thiollier).
    Le musée Albert Kahn est loin d’être le seul à avoir de telles collections, il y a aussi Orsay, la SFP ,

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  29. Pingback: Wat is geohashing? | frevanoers.be

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  48. Geohash is a latitude/longitude geocode system invented by Gustavo Niemeyer when writing the web service at geohash.org, and put into the public domain. It is a hierarchical spatial data structure which subdivides space into buckets of grid shape.
    Geohashes offer properties like arbitrary precision and the possibility of gradually removing characters from the end of the code to reduce its size (and gradually lose precision).
    As a consequence of the gradual precision degradation, nearby places will often (but not always) present similar prefixes. Conversely, the longer a shared prefix is,

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