What We Did Last Tuesday: A Geohashing Primer

So last week I was attempting to boast of a great feat of geohashing daring-do, although the message might have been lost in my amateurish attempt to channel James Joyce and in all of the parochial geographic references. Basically, I drove around the region all weekend, occasionally leaping out of the truck to tromp around in the underbrush. So doing, I successfully hit 6 out of 6 "hashpoints" (see below), a rare achievement indeed.

But to top things off, I went and did another impossible thing (albeit not before breakfast) two days later. Before I direct you to the gory details, though, perhaps I ought to explain to the puzzled among you how this "geohashing" thing works.

Some Definitions

To start with: as you know, there is an abstract grid of lines draped o'er the globe for purposes of navigation and for locating stuff. Degrees of latitude indicate relative position north and south, and degrees of longitude indicate position east and west. As you may well have forgotten, these degrees are subdivided, like hours of time, into sixty minutes('), and those minutes into sixty seconds("). So a landmark -- Ayers Rock, let's say -- can be located at 25° 20' 44" S 131° 2' 1" E. (Actually, that's just one little spot on the immensity of Ayers Rock, but you get the idea.)

Finally, as you probably never knew in the first place, the square rectangular roughly rectangular (usually) portions of the Earth's spherical surface (phew!) that are bounded by latitude and longitude lines are called graticules. Here's an example from my customized geohashin' map of Oregon, showing in black lines the graticules bounded by the local lines of latitude (44 N, 45N, 46N) and longitude (121W, 122W, 123W, 124W).


Hashpoints

Every day, a random set of coordinates is generated for geohashers. How is not important, except in that (a) it is truly random and (b) the random number generator is seeded by the date and the opening value of the Dow Jones Industrial index. This latter is also not important, except in that -- because the American stock market is closed on weekends and on American holidays -- you get the coordinates for Saturdays, Sundays, and American holidays a day or two in advance, instead of at 9:30 Eastern Time on the day of.

These coordinates locate a "hashpoint" for that day within your graticule. The coordinates are in the same relative position within each of the world's bazillion graticules (with a few asterisks tacked on here for the equator and so on, for those of you who groove on spherical geometry). So, a given day's hashpoints might be distributed like so here in northwest Oregon:

...except that hashpoints are literal points, not big areas like those orange circles would imply.

OK, Random Locations. So What?

Well, the goal of course is to try to GET to the random locations. "Why?" you might well ask, and it's a fair question, and all I can say is that if you are asking it than geohashing is probably not for you. I can only assure you that there is a very limited number of people living among you who do not ask "Why?" but rather say "Oh my god, where do I sign up?" (One "signs up," as it were, here.)

You will quickly discover, though, that more often than not you will not actually be able to get to your local hashpoint. This is not because Obama is taking away your freedom(?), but rather because most places are simply not accessible. This will vary depending on where you live -- indeed, one of the cool things about being a geohasher is that the daily checking of the hashpoints teaches you a lot about the composition of the landscape you live in -- but in the Portland, Oregon graticule, for instance, we get a lot of hashpoints that fall in practicably impenetrable forests, in cropland, and in people's houses or backyards. We also get a fair number that fall in lakes and rivers, which doesn't rule out a successful expedition but which brings up the need for a boat or strong swimming skills.

If you've determined that a hashpoint is potentially accessible, then off you go! If you are a social type, you might try to get to the hashpoint at the same time as other people (although with only a few hundred active geohashers worldwide, your odds aren't good). As this is a game played by confirmed dorks, however, there are plenty of merit badges available for various ways of reaching the point (by bike! without crossing your own path! at the legal speed limit! in fancy dress! etc.!).

For a while, I was content to use online aerial imagery and my surveying skillz to find hashpoints. We have so much forest cover in the Beaver State, though, that eventually I felt the need for a GPS gadget. This was not a trivial expense, but it has quickly become one of my favorite toys ever.

There are unfortunately some real barriers to entry to the hobby. The main one is that, to really be participating, you need to write up your adventures on the geohashing wiki. That's kind of time consuming, and forces you to learn wiki coding. But it's kind of fun, too.

Frequently Asked Question That Reveals That the Person Asking the Question is Wrestling with the Concept

Q: So what do you find at the hashpoint?

A: Nothing, of course. It's a random point, so unless someone else got to the hashpoint earlier in the day and left something for you to find, you will just find the location, wherever it is, as it is. Here's the hashpoint I'm about to tell you about:

Nothing to find. If you want to find something on your adventures, then you need to talk to the geocacheing people. There's a lot more of them, but their hobby is kind of... I don't know... cut and dried for my taste.

What We Did Last Tuesday

So when I woke up and checked the hashpoint in the morning, as one does, I saw that it was waaaay in the very southeast of the graticules (in the northern and western hemispheres, anyway). Which made me immediately look at the North Lincoln City graticule. Here's the North Lincoln City graticule on my geohashin' map:

It is well over 99.9% ocean. But last Tuesday -- 2010-08-31, as we call in on Planet Geohashing -- the hashpoint fell on the tiny, tiny sliver of land at its extreme southeast. So obviously Mrs.5000 and I took the afternoon off work and went out adventuring.

Here's the writeup: http://wiki.xkcd.com/geohashing/2010-08-31_45_-124

It's a story with a happy ending:

OK, I'm sure you're convinced. See you at the hashpoints!