As far as I understood, you take 3 input variables, date, the DOW () opening, and location coordinates.
Then you get the date and dow's number hashes using md5 (http://en.wikipedia.org/wiki/MD5). You get two alpha-numeric strings. Each string is then taken to a (numeric) decimal system. Let's call this two numbers D1 and D2.
Now we take the location coordinates. We truncate them to get rid of decimal numbers. This two numbers will be, say, X and Y.
Finally, the output of the process are two numbers (coordinates), X+D1, and Y+D2. This coordinates are quite random.
So given coordinates, and a date, depending on the DOW opening of the day you calculate it, you get new coordinates.
Blag entry at XKCD: http://blag.xkcd.com/2008/05/21/geohashing/ |
I mean I got the formula, but not the use?
Not even in the comic sense :( |
I end up in the middle of the sea.... Hmm maybe doing this on the South coast of England isn't such a good idea :-) |
Well, I took it to mean you go Geocaching but you pick the destination by Geohashing. Instead of looking for somewhere people have already been, you just run the formula from the comic and it gives you a destination to go. |
Here's a description from their wiki:
<<XKCD comic #426 contains an algorithm that generates random coordinates across the country1 every day.
These coordinates can be used as destinations for adventures, a-la Geocaching. They can also be used for local meetups. (...)
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.>>
http://wiki.xkcd.com/geohashing/Main_Page |
A mostly natural progression from the earlier comic:
http://xkcd.com/240/
That resulted in a gathering out in North Cambridge, MA. |
