Main Page

The Algorithm

Coordinates for Portland on January 1, 2008 (taken from this tool)

NoTerminal and Drache at the February 17th coordinates

What is this?

XKCD comic #426 contains an algorithm that generates random coordinates across the country¹ every day.

These coordinates can be used as destinations for adventures, à la Geocaching. They can also be used for local meetups.

For a little more interactive discussion consider joining the #geohashing IRC channel on Foonetic.

^1. Europe/Asia date handling still under discussion, see Talk:Main Page.

How it works

Play with the coordinate calculator here: http://xkcd.com/geohashing

Every day, the algorithm generates a new set of coordinates for every region. They are randomly placed -- they could be in the forest, in a city, or on a mountain. You can use this wiki to document the coordinates (geohashes) you've been to.

Unless you can predict the stock market, you can't figure out what the coordinates will be ahead of time. You can first calculate a weekday's coordinates at about 9:30 AM (Eastern), and on Friday morning you can calculate the coordinates for each day that weekend.

If you go on Saturday afternoons, you might encounter other xkcd readers. Bring games!

When the coordinate falls somewhere dangerous or illegal to reach, use your judgment. If the coordinates are in an obviously unreachable place (e.g., ocean), the meetup is postponed until a better day. Alternatively, rent a boat.

Official Meetup

The official xkcd meetups happen every Saturday afternoon at 4:00 PM (local destination time). If the coordinates for your area are in the ocean, a military base, or somewhere otherwise unreachable, that meetup is of course postponed. Unless, of course, you own a boat, are a soldier at said military base, or are James Bond. If you can, record who's there, take pictures, and post them here.

Implementation

A sample interactive coordinate calculator can be found here: [1] A reference implementation is available here: view download

A python implementation:

import md5, datetime, struct, urllib, re
date = datetime.date.today()
djia = urllib.urlopen(date.strftime("http://irc.peeron.com/xkcd/map/data/%Y/%m/%d")).read()
sum = md5.new("%s-%s" % (date, djia)).digest()
print struct.unpack(">Q", sum[0:8])[0] / (2.**64), struct.unpack(">Q", sum[8:16])[0] / (2.**64)

There is also a Python package xkcd.geohash which is independent of the interactive coordinate calculator (but uses Google Finance as well).

Yet another implementation in Python is here as well. It does the same as the ones above but also gives "validation" information. Lets you know if the geohash location is under water and thus if its a valid place to go party :). I'll add more terrain recognition if people like it. A webservice to access it can be found JSON Web Service and an application using the web service can be seen here Application. The code is over here Source Code

If you're looking to code your own utilities and need a source for the Dow Jones Industrial Average for a day, NuclearDog has set up a mySQL backed page to query the value that automatically updates hourly. Details on this service (and others) is available at Dow Jones Industrial Average.

Atom feed

You can subscribe to a feed that will give you updates on a daily basis:

http://staticfree.info/geohash/atom/LAT,LON

For example, here's the Atom Geohash for Boston.

Just put your coordinates in, subscribe and you'll be ready to go!

Active Graticules

See Active Graticules for a list of graticules with active users in them.

Recent Expeditions

2008-05-21 42 -71 -- User:Xkcd and cousin Annuska reached the Boston coordinates and photographed a spider.

2008-05-17 37 -122 -- Dan, Emad, and Randall reached the San Francisco coordinates in a successful test.

2008-02-24 45 -122 -- NoTerminal and Drache reached this point as part of an early test while coming up with the algorithm.

Next Upcoming Day

2008-05-21 -- The coordinates for Wednesday, May 21st are available.

Next Saturday

2008-05-24 -- The coordinates for Saturday, May 24th will become available on Friday about 9:30 AM EDT, when the Friday Dow Jones opening price is published.

See TimeandDate.com for Dow opening time in local time zones.

Note that complications may arise due to timezones - not to mention both spatial and temporal abnormalities. (I.e. Individual results may vary.)

Related Projects

Geocaching: Global GPS cache hunt

Geodashing: Monthly points, randomly created

The Degree Confluence Project: visiting every integer latitude/longitude crossing point in the world