Implementations

Definition

An implementation is a program that takes the method shown in The Algorithm to calculate the geohash location, presenting the user with text coordinates, a map, data for a navigation device, or some other information that facilitates reaching the geohash.

If you're looking to code your own utilities, you will need a source that provides the Dow's opening price for any given day. Details on such services are available at Dow Jones Industrial Average.

Official Implementations

Interactive Coordinate Calculator

This implementation IS FULLY 30W-compliant.

The original sample interactive coordinate calculator can be found at http://carabiner.peeron.com/xkcd/map. Here are some notes on Using the Coordinate Calculator. The common URL, http://xkcd.com/geohashing, redirects here. Any problems or issues should be mentioned to Zigdon either on the wiki or in the [#geohashing channel on irc.foonetic.net], as well as posted at Talk:Implementations.

Reference Implementation

This implementation IS FULLY 30W-compliant.

A reference implementation is available:

view download

It cannot automatically apply the 30W rule, as it doesn't take your location into consideration. If you're East of 30W, call it with the -e option and it will yield the correct results.

Any problems or issues should be mentioned to Zigdon either on the wiki or in the [#geohashing channel on irc.foonetic.net], as well as posted at Talk:Implementations.

Geo::Hashing on CPAN

This implementation IS FULLY 30W-compliant.

Reusable code library that can be used from any perl program:

Geo::Hashing Sample code

MediaWiki Implementation

This implementation's 30W-compliance is tied to that of another implementation. See notes.

MediaWiki half-implementation (for use by template creators).

Python Implementations

Python Implementation 1

This implementation IS FULLY 30W-compliant.

import hashlib, datetime, struct, urllib, re, sys
date = datetime.date.today()
djia = urllib.urlopen((date - datetime.timedelta(w30)).strftime("http://carabiner.peeron.com/xkcd/map/data/%Y/%m/%d")).read()
if '404 Not Found' in djia: sys.exit(sys.stderr.write("Dow Jones not available yet.\n"))
sum = hashlib.md5("%s-%s" % (date, djia)).digest()
lat, lon = [x/2.**64 for x in struct.unpack_from(">QQ", sum)]; print lat, lon

• In the above, w30 on line 3 should be replaced by 1 if you're east of -30°, and with 0 otherwise.
• As md5 has been deprecated in favor of hashlib since python 2.5, if you are using python 2.4 or earlier, substitute hashlib for md5.
• To generate globalhashes, set w30=1 and multiply the final lat, lon values as indicated on that page.

Python Implementation 2

This implementation IS FULLY 30W-compliant.

import hashlib, datetime, struct, urllib, re, sys, webbrowser
myLat = 34
myLon = -87
args = sys.argv
if len(args) == 1:
    args.append(myLat)
    args.append(myLon)
else:
    args[1] = int(args[1])
    args[2] = int(args[2])
if args[2] < -30:
    td30 = 0
else:
    td30 = 1
if args[1] < 0:
    south = -1
else:
    south = 1
if args[2] < 0:
    west = -1
else:
    west = 1
date = datetime.date.today()
djia = urllib.urlopen((date - datetime.timedelta(td30)).strftime("http://carabiner.peeron.com/xkcd/map/data/%Y/%m/%d")).read()
if '404 Not Found' in djia: sys.exit(sys.stderr.write("Dow Jones not available yet.\n"))
sum = hashlib.md5("%s-%s" % (date, djia)).digest()
n, w = [str(d*(abs(a)+f)) for d, f, a in zip((south, west),
    [x/2.**64 for x in struct.unpack_from(">QQ", sum)], args[1:])]
print n, w
dest = 'http://maps.google.com/maps?f=q&hl=en&geocode=&q=' + n + '+' + w + '&ie=UTF8&ll=' + n + ',' + w + '&spn=0.918082,1,864929&z=9&iwloc=addr'
print dest
webbrowser.open(dest)

• The above code is based on the earlier sample code, and is subject to the same provisos regarding md5 and hashlib.
• You can set the myLat and myLon variables on lines 2 and 3 to your latitude and longitude, and invoke the code directly.
• You can also save the code to a module (e.g., geohash.py) and invoke it like this: python geohash.py 34 -87 (substituting my example with the latitude and longitude of your choice).

Python package xkcd.geohash

This implementation IS NOT 30W-compliant.

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

RESTful Python implementation with Atom feed

This implementation IS FULLY 30W-compliant.

This implementation uses web.py to give simple, clean URLs.

The source for the Atom feed is available through anonymous svn here: https://staticfree.info/svn/ghfeed/ To contribute to it, please contact xxv and he can set you up with commit access.

Hackish Bitcoin-based Python Implementation

This implementation IS NOT 30W-compliant.

MarkTraceur made this to test what Geohashing would look like using a different financial source. It's based on the opening price of Bitcoins in USD at Mt. Gox. You can change the site you use, the coordinates, or just about anything pretty easily. It will get nicer-looking as time goes on.

It is here: https://github.com/MarkTraceur/geohash-btc

Feel free to fork it and/or send feedback through GitHub!

Shell Script Implementation

This implementation IS FULLY 30W-compliant.

#!/bin/sh -e

command -v md5 >/dev/null 2>&1 || md5() { md5sum | cut -c 1-32; }; [ -n "$1" ]
command -v GET >/dev/null 2>&1 || GET() { wget -qO - "$@"; }; [ "$2" -gt -30 \
] && { date -R >/dev/null 2>&1 && y='-d yesterday' || y='-v -1d'; }; d=$(GET \
carabiner.peeron.com/xkcd/map/data/$(date $y +%Y/%m/%d)); printf $(date $3 +%F-$d) |
md5 | sed 'y/abcdef/ABCDEF/; s/.\{16\}/.&LgPp/g' | dc -e "[$2]Sg [$1]Sg 16i" -

Pass your graticule's lat and long as the arguments to the script. (A third argument may be used to manipulate the date, if you know what you are doing. This is not useful for much more than getting Saturday's hash on Friday.) If something fails it will exit with a nonzero status.

This works with GNU/FreeBSD date, lwp or wget, and bash/ksh/ash, but not OpenBSD date or curl (which are missing some of the features abused here). It would theoretically work with fetch but I removed that for the sake of brevity. Suggestions are welcome, as well as reports of compatibility with other operating systems or implementations of dc.

Here is a contributed wrapper script that will set default co-ordinates for you and call the above implementation, then attempt to print the answer as a Google Maps URL. On OS X, it will launch the URL, but on other operating systems weird things might happen. It has been edited to assume that the first script is installed as "geohash".

#!/bin/sh

if [ $# -lt 2 ] ; then  # Put your default geo-coords here
    : ${LAT:="36"}
    : ${LON:="-122"}
else
    : ${LAT:="$1"}
    : ${LON:="$2"}
fi

showGeoHash()
{
    echo "${1} ${2}"
    echo "http://maps.google.com/maps?q=${1}+${2}"
                                                        ######## Comment all but one of the following lines.
    open "http://maps.google.com/maps?q=${1}+${2}"      # For Mac OS X.
    firefox "http://maps.google.com/maps?q=${1}+${2}"   # For other *nix with Firefox installed in $PATH.
}

showGeoHash $(geohash $LAT $LON)

Alternative geohash location suggester

This implementation IS PARTIALLY 30W-compliant. not compatible for dates before 2008-05-27

Geohash Recommender - This website doesn't seem to work as of 12J-un-09

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. Using this it attempts to suggest the "best" alternative geohash by checking all neighbouring grid locations. I'll add more terrain recognition if people like it. The code is over here Source Code

Bugs

• There are a few, it needs a few refreshes to get the whole tagging right. It also has trouble guessing the terrain type occasionally. Refreshing it makes it work but its a problem im looking into, have a look at the code and help if you can :)
• Gives me a false location for May 28 and 29, 2008, which aren't yet known anywhere in the world according to the algorithm. --Tim P 21:29, 24 May 2008 (UTC)
  • But... thos dates aren't real yet. There is no dow result. Granted it should give an error instead of giving _something_ but...
    • As of 05:06, 26 May 2008 (UTC), this gives locations for May 27-30 west of 30W and for May 28-31 east of 30W, i.e., four days beyond what should be calculable as of that time. Beyond those dates, it gives a proper error message stating that no Dow is available. I think temporary data were added to the implementation for testing purposes; these should be removed. --Tim P
    • One could interpret the algorithm such that, for any date in the future, one is to use "the opening price from [DOW's] previous day of active trading is used", i.e., the most recent trading day. Obviously, this would lead to the location changing as the day approaches but, in a random spontaneous adventure generator, that seems almost mathematically pure. I mean, that's just what happens when you try to generate spontaneity too far into the future, yes?  ;) Ted 00:19, 30 May 2008 (UTC)
• Electronicwar website seems to be no longer functioning. Jiml 00:29, 13 June 2009 (UTC)

Comic Creator

This implementation IS FULLY 30W-compliant.

A python class to recreate the original comic, but for any given date with your own coordinates! Below shows the comic for the first North East Netherlands meetup. Although it fetches the Dow itself, you can add &dowjones=12345.67 if it doesn't do so correctly (e.g., peeron.com is down). Created by Hugo.

http://www.astro.rug.nl/~buddel/cgi-bin/geohashingcomic/geohashingcomic.cgi?year=2008&month=5&day=24&lat=55.218512&lon=6.566854

You can download the script as well if you wish.

In the image, Dow values less than 10,000.00 are padded with leading spaces, however in the algorithm it is not so it is compliant with other the algorithms. As Tim P suggested, the comic is akin to all the bank cheques with "19__" printed on them being used in 2000. The "form" has 5+2 "boxes" because that's how Dow prices are now, but that doesn't mean it can't be different.

Oh, goodness. Aren't we glad we took care of that before the Dow lost 24% in a month?  :) --Tim P 04:14, 10 October 2008 (UTC)

Bugs

• The font sizes are not exactly as the original and there can still be some alignment problems.
• The -0 issue is ignored. Only if you enter -0 as an integer you get an incorrect outcome. You are supposed to enter your own location as a float, up to 6 decimals, everything is okay even when you enter -0.0.

Semi-manual offline calculator

This implementation IS FULLY 30W-compliant.

If you're going to be away from internet access, you'll need to compute the hash locally:

• Download and extract this: http://lab.brainonfire.net/drop/geohash-offline.zip
• Working example: http://lab.brainonfire.net/geohash-offline/calc.html

Notes

• All you need is a Javascript-enabled browser. Tested in Firefox so far.
• You will have to somehow acquire the Dow's opening value for the appropriate date; there may be a service to do this.
  • Remember, if you're east of 30W, you should use the previous day's opening price, even if a new one becomes available later in the day.
• The date is filled in automatically using the current timestamp.
• You'll have to combine the computed fractional coordinates with your graticule coordinates yourself.
• I grabbed MD5 and base conversion code from random internet sites.

Text Messaging (email) service

This implementation IS FULLY 30W-compliant.

If your cell phone supports text messaging to an email address, you can get geohash updates on your phone by sending a formatted text to srv@geohash.info

Formatting

YYYY-MM-DD Lat Lon Example:

2008-02-18 42 -83

Alternatively, it defaults to the current date (EST for now) and you can just enter Latitude and Longitude

42 -83

Bugs

• The -0 Issue is still very much an issue.
• This used to display the degree symbol after coordinate elements, but due to poor cell phone support of this character, which resulted in messages cutting off after the first Latitude, I have removed it.
• This is also not a terribly robust solution, but a better (stronger, faster) implementation is in the making.
• Not necessarily a bug, but a desirable feature: it would be nice to be able to omit the '-' character when specifying the date (it just happens to require many keystrokes to type - on my phone)

Text Messaging service (SMS)

This implementation IS FULLY 30W-compliant.

Text "GH [date]" to +41774378210, eg:

gh 20091110

A few seconds later you should get an sms response similar to the following:

Relevant DJIA for 2009-11-10 is 10223.01(W) / 10020.62(E). Decimal parts are: 0.02335 0.228005(W) / 0.854495 0.149983(E).

Occasionally you may see a result of <n/a> when information is unavailable. For example, if you are looking at a date where coordinates are only available east of w30, you may see something like:

Relevant DJIA for 2009-11-10 is <n/a>(W) / 10020.62(E). Decimal parts are: <n/a>(W) / 0.854495 0.149983(E).

Not case-sensitive, so "Gh", "gh" etc. are all fine. Don't forget the space between "gh" and the date. The script is also flexible on the date format as long as it's in the Y-m-d order.

The service uses the DJIA source that I maintain.

I recommend testing it once before you are away from home and really need it. Also, don't hesitate to tell me if you don't get an sms back or if you feel that something else is not working properly...

See also SMS DJIA service; suggestions, comments and other feedback to User:Crox.

Local email tool in D, for Linux

This implementation IS FULLY 30W-compliant.

Run this program once a day (for instance, per crontab) to get email notification whenever Google Maps indicates the daily target is nearer than a specified range. The first time around, run it from the commandline to configure. Configuration is stored in ~/.geohash/geohash.cfg. Use --help for info about commandline parameters. Source. Linux 32-bit upx compressed binary.

Feeds

GeoRSS feed

This implementation IS NOT 30W-compliant.

You can subscribe to a feed (in GeoRSS format) that will give you updates on a daily basis^{[citation needed]}. Updates include the "best guess" address of the location as well as the specific latitude/longitude coordinates.

http://atlas.freshlogicstudios.com/Features/Experiments/Xkcd/Xkcd.ashx?Latitude=38&Longitude=-91

For example, here's the GeoRSS geohash for St. Louis.

This GeoRSS feed is used to power the Atlas geohash implementation.

Atom feed

This implementation IS FULLY 30W-compliant.

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!

Source is available from subversion: https://staticfree.info/svn/ghfeed/

Atom Feed Bugs

• I noticed yesterday that before the stock exchange data becomes available, the atom feed creates a kind of 'intemediary' geohash using todays date and yesterday's data. This might be intentional, but personally I find that undesirable on weekdays. Could it be modified to show yesterday's date and geohash until data is available? Nicktaylor 14:04, 23 May 2008 (UTC)
  • It's definitely broken. -- Phyzome 11:37, 28 May 2008 (UTC)
    • This implementation was written before the 30W rule. As it turns out, the intermediate hash falls back on the previous Dow while using the current date from 00:00 (local) to 09:30 ET, which happens to be the desired 30W behavior. However, this is not helpful west of 30W. An inverse problem occurs after 09:30 USET east of 30W, until 24:00 local. See detailed discussion at Talk:Implementations#Atom feed 30W-compliance. --Tim P 15:45, 29 May 2008 (UTC)

geohash.info

This implementation IS FULLY 30W-compliant.

Subscribe to a feed that updates as soon as each day's meetup is calculable for your graticule:

http://www.geohash.info/srv/feed.php?lat=LAT&lon=LON

If you visit the URL with no parameters, you will be prompted for your graticule coordinates.

• Dow data comes from the peeron service
• To view source, drop the parameters and change the extension to .phps -- this currently works for all PHP files in geohash.info/srv/

Quirks

• The script estimates your timezone based upon your longitude, and uses -04:30 as the timezone of the Dow. Therefore, the update times may be off by as much as an hour or two. Shouldn't be an issue, since they'll be around midnight for most people.
• For non-30W users, the feed will be empty between midnight and 9:30 AM -- this should be acceptable, since most feed readers keep entries that have dropped off the end of the feed. (This behavior may be changed in the future.)

Flickr

This won't help you find future (or, likely, present) coordinates, but one can keep tabs on photos that users have tagged with geohashing at Flickr by using this RSS feed link.

Geo Hashing RSS

This implementation IS FULLY 30W-compliant.

Another RSS implementation, coded by Matty K. This one simply provides a graticule's coordinates for a given day, and gives links to both Google maps and the peeron maplet. It is recalculated at every request (so please don't hammer it, or my website will run out of bandwidths).

http://geohashing.kerwin.net.au/rss.php?ll=LAT,LON

For example, the link for San Francisco's feed is: http://geohashing.kerwin.net.au/rss.php?ll=37,-122

Notes:

• If latitude/longitude are not given, it defaults to my home graticule .
• I don't know if it supports negative zero. If there is a request to add specific support, please let me know. I added specific negative zero support, and tested it with the London area. It appeared to work okay.
• 30W-compliance is based on the fact that I live East of 30W, and it gives me the right coordinates each day.
• For any bug reports or other features requests, please email Matty
• Sources can be made available by request. Although Matty might be a little ashamed of the shoddy code.

k4 implementation

This implementation IS NOT 30W-compliant.

Here's an implementation in k4, a vector-programming (i.e., self-obfuscating) language that seems to me to be very true to the spirit of xkcd. The following shell script takes the graticule as an argument, uses standard standard unix tools to retrieve the current Dow opening price, and returns a URL for a Google map to the the upcoming Saturday's meetup. It assumes the q executable is in your PATH.

#!/bin/sh

test $# -eq 2 || exit 1
dow=`curl -s 'http://finance.google.com/finance?cid=983582'| \
 egrep -o '<span id="ref_983582_op">[^<]+</span>'| \
 sed -r 's/.*>(.*)<.*/\1/'|tr -d ,`

q -lat $1 -lon $2 -dow $dow<<"EOF"
\
(.q.set').(!:;,/)@\:.Q.opt .z.x;
h:.Q.n,6#.Q.A;c:16 xexp'-:'1+!16
u:"http://maps.google.com/maps?q="
d:.q.ssr[$.z.D+7-.q.mod[.z.D]7;".";"-"]
s:0N 16#,/$-15!"-"/:(d;dow);l:(lat;lon)
-1@u,"+"/:l,'1_'$sum'(h?/:.q.upper s)*\:c;
\\
EOF

For example, here's New York as of 2008-05-23:

% gh 40 -74
http://maps.google.com/maps?q=40.126648+-74.5475331

N.B., this was written on a Friday; I make no guarantee that it will produce useful results when run on any other day of the week (though Saturdays will probably work).

Adavies42 20:50, 23 May 2008 (UTC)

Automatic GPX File Generator

This implementation IS NOT 30W-compliant.

I have modified the sample perl implementation so that it automatically generates a .gpx file which you can upload to your favourite GPS device/software. Download here Before you use the script, you need to modify it and put your own lat/lon values into the corresponding variables at the beginning. ~~Wansti

GeohashGenerator for Popfly

This implementation IS FULLY 30W-compliant.

I have created a Popfly block to use for creating mashups at http://www.popfly.com/users/rbuckton/GeohashGenerator. Can be integrated with Virtual Earth, etc.

rbuckton

Lazy Geohasher

This implementation IS PARTIALLY 30W-compliant.

If you'd rather just stay at home and wait for a geohash to come to you (or perhaps have some other reason to participate in Geohash Hacking), there's a perl script which will search for combinations of times and DOW Jones opening prices to find when you could win the much coveted Couch Potato Geohash or Cubicle Geohash award. Just put in the ranges of values for the stock market and the time you want to wait for, and watch those CPU cycles fly! -- thaniel.drake@gmail.com.

30w compliance statement: This code does not use live data. Users are expected to determine from the date of the Geohash which opening value is relevant for their locale.

Disclaimer: The author humbly requests that you do not manipulate the Dow Jones Industrial Average to ensure that a geohash collides with your address. The author accepts no responsibility for any resulting financial instability you cause by such manipulations.

Here is an improved implementation which sorts results by great-circle distance. Distance cutoff, length of search, and dollar spread searched may be adjusted at the command line. Days may be a positive integer count of days following today or a comma-separated list of %F datespecs. Same 30W caveats apply.

This implementation IS PARTIALLY 30W-compliant.

#!/usr/bin/perl -w
require 5.9.2;

use Digest::MD5 qw(md5);
use POSIX qw(strftime);
use Math::Trig qw(deg2rad great_circle_distance);

die "usage: $0 lat lon orig-dow [spread] [days] [max-km]" unless @ARGV >= 3;
my ($lat, $lon, $orig, $spread, $days, $max_km) = @ARGV;
my ($g_lat, $g_lon) = map { int } $lat, $lon;
$spread ||= 500; $days ||= 7; $max_km ||= 1;

sub geohash { map { $_ / 2**64 } unpack("Q>Q>", md5(shift)) }
sub genday {
    my $date = shift;
    for (($orig - $spread) * 100 .. ($orig + $spread) * 100) {
        my $dow = sprintf("%.2f", $_ / 100);
        ($f_lat, $f_lon) = map { substr($_, 1) } geohash("$date-$dow");
        $gh{"$date-$dow"} = [$g_lat . $f_lat, $g_lon . $f_lon];
    }
}

if ($days =~ /^\d{4,}-\d{2}-\d{2}/) { genday($_) for split(/,/, $days) }
else { genday(strftime("%F", localtime(time + 86400 * $_))) for (1...$days) }

sub d2r { deg2rad($_[0]), deg2rad(90 - $_[1]) }
sub gdist { great_circle_distance(d2r($lat, $lon), d2r(@{$_[0]}), 6378) }

printf "%s -> %f,%f (%.3fkm)\n", $_->[0], @{$gh{$_->[0]}}, $_->[1] for
    sort { $a->[1] <=> $b->[1] }
        grep { $_->[1] < $max_km }
            map { [$_, gdist($gh{$_})] } keys %gh;

For discussion of the actual algorithm stuff hiding in there, please see the next section.

Alternative Perl Implementation

Because there is no way this page is complete without a lesson on endianness...

In writing the above "lazy" script I needed to come up with a way to do the actual hashing in Perl. So, here it is pulled out from that, and using today's data from the web service:

This implementation IS FULLY 30W-compliant.

#!/usr/bin/perl -w
require 5.9.2;

use POSIX qw(strftime);
use LWP::Simple;
use Digest::MD5 qw(md5);

die "usage: $0 lat long" unless @ARGV == 2;
my @graticule = map { int } @ARGV;

sub dow_open {
    my $date = strftime("%Y/%m/%d", localtime(shift));
    get("http://carabiner.peeron.com/xkcd/map/data/$date");
}

sub geohash {
    map { $_ / 2**64 } unpack("Q>Q>", md5(shift));
}

my $today = strftime("%F", localtime);
my $dow = dow_open(time - ($graticule[1] > -30 ? 86400 : 0));

for (map { substr($_, 1) } geohash("$today-$dow")) {
    print shift @graticule, $_, "\n";
}

This is the same bare output format as the shell script, for piping into your favorite formatter or google-launcher or whatever. The reason it requires Perl 5.10, however, is the code used to interpret the hash:

map { $_ / 2**64 } unpack("Q>Q>", md5(shift))

One unfortunate thing I have noticed across implementations is that a lot of effort has been spent converting hexadecimal into decimal. It is important to remember that MD5 hashes are 128 *bits* -- hexadecimal is just a form of representation. (It's very convenient, and we see it everywhere. But even in the original comic, it's representation.) In languages that provide the power to deal with data directly, the familiar hex representation can frequently be skipped in our quest to present numbers as decimal. This is what unpack does above (The Python implementation uses their flavor of unpack as well. I am sure Ruby has something similar).

I point this out only because Perl neglected to get this right until recently, and so the code as written will not run on 5.8 or earlier. As they are presented in the algorithm, the two 64-bit binary fractions (think: 1/2's place, 1/4's place, 1/8's place... with the caveat that we only see the numerator digits; the denominators are all 1!) from the 128 bits of MD5 are big-endian. Sadly, the machine running Perl might be big-endian or little-endian (think: the first 8 places at the end, then the next 8 places before that, etc... it's reversed by bytes, not bits). 5.10 provides the "<" and ">" endianness specifiers for all types, even 64-bit numbers. But on 5.8, attempting to directly grab the bits will always use the machine's native arrangement, and so only work if you're in big-endian-land. Most of us (running x86 CPUs) are not. Here is one (ugly) way to deal with it:

map { $_ / 2**64 } reverse unpack("QQ", reverse md5(shift));

Evaluation works backward from the right; by reversing the byte string (remember how it's backwards by bytes? the word that looks forward to us looks backward to them, too), we are able to unpack two 64-bit chunks that *would* be the right numbers, but are now (since the whole thing was reversed) in the wrong order, so we flip them around again. If they weren't the same sizes, we would have had to reverse the unpack specification as well (in fact, we did; you just couldn't tell). Fun, no? So if you need to run this on 5.8, patch this in and remember to delete the "require" line.

All-Time Closest Geohash to Where You Lived At The Time

This implementation IS FULLY 30W-compliant.

This Perl script takes as its input a comma-separated text file giving the starting and ending dates and latitude and longitude of every place you've ever lived (or worked, or any other place you're interested in), and finds the closest hashpoint ever to come to any of those places while they were current for you. See if you have a retroactive Couch Potato Geohash somewhere in your history! (You're out of luck if you lived anywhere before 1928-10-01, though, since that's as far back as the data goes.)

#!/usr/bin/perl -w

# Program to find nearest historical geohash to place(s) you're interested
# in, such as your homes or workplaces.  As it goes forward through the
# dates it's checking for hashes in, it outputs each one that sets a new
# record for closest yet to a place of interest.

use strict;
use Geo::Hashing;

# set current date
my $currdate = sprintf("%04d-%02d-%02d", (localtime)[5]+1900,
                                         (localtime)[4]+1,
                                         (localtime)[3]);

# Initialize extremes so they're later replaced by actual values
my $mindate = $currdate;
my $maxdate = '1928-10-01';

# Read in places and dates of interest.  File should have all the locations
# you want to check for nearby past geohashes in, such as all the places
# you've ever lived (or worked), with the date range for each.
# Date ranges may overlap, so you can track multiple homes/workplaces at once.
# Put in file places.csv in same directory as this script
# Each line is in format: FromDate, ToDate, Latitude, Longitude, Title
# Dates are in form YYYY-MM-DD
# Lat/Lon are in decimal degrees, negative numbers for W / S
# Empty FromDate means 'from beginning of time', 1928-10-01 in this case
# Empty ToDate means 'until present', going up to and including current date

my $i = 0;
my @fromdate = ();
my @todate = ();
my @lat = ();
my @lon = ();
my @title = ();
open INFILE, "<places.csv" or die "You must create a places.csv file in the same directory as this script.
This is intended to contain a list of every place you've lived
(or worked, etc.), by date and location.
Format: 1 line per place
FromDate,ToDate,Latitude,Longitude,Title
Dates in format YYYY-MM-DD
Lat/Lon in decimal degrees
Title is whatever text string you want to identify a place with.\n";
while (<INFILE>)
{
  chomp;
  ($fromdate[$i], $todate[$i], $lat[$i], $lon[$i], $title[$i]) = split(/\,/);
  $fromdate[$i] = '1928-10-01' if !$fromdate[$i];
  $todate[$i] = $currdate if !$todate[$i];
  
  $mindate = $fromdate[$i] if $fromdate[$i] lt $mindate;
  $maxdate = $todate[$i] if $todate[$i] gt $maxdate;
  
  $i++;
}
close INFILE;

my $latmiles = 69.1703234283616; # Conversion factor of lat degrees to miles; always constant

my @MonthLen = (0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);

my $date = $mindate;
my ($yr, $mo, $dy) = split(/-/, $date);
$MonthLen[2] = 29 if &is_leap($yr);

my $mindist = 9999; # Initialize min distance to high number

while ($date le $maxdate)
{
  for ($i = 0; $i<=$#fromdate; $i++)
  {
    if ($date ge $fromdate[$i] && $date le $todate[$i])
    {
      my ($lat, $lon) = (int($lat[$i]), int($lon[$i])); # Integer lat/lon for hashpoint lookup
    
      my $geo = new Geo::Hashing(lat => $lat, lon => $lon, date => $date); # Get hashpoint for date
      
      my $latdiff = abs($geo->lat - $lat[$i]); # Find absolute distance in each axis direction
      my $londiff = abs($geo->lon - $lon[$i]);
      
      my $lonmiles = 69.1703234283616 * cos($lat[$i]*0.0174532925199433); # Conversion factor of lon degrees to miles
      my $latdiffmiles = $latdiff * $latmiles; # Convert to miles
      my $londiffmiles = $londiff * $lonmiles;
      
      my $distance = sqrt($latdiffmiles**2 + $londiffmiles**2); # Find hypotenuse
      
      if ($distance < $mindist) # Found new shortest distance so far
      {
        $mindist = $distance;
        printf "$date: %0.6f, %0.6f -- %0.4f miles from $title[$i]\n", $geo->lat, $geo->lon, $distance;
      }
    }
  }
  
  # Advance date
  $dy++;
  if ($dy > $MonthLen[$mo])
  {
    $dy = 1;
    $mo++;
    if ($mo > 12)
    {
      $mo = 1;
      $yr++;
      if (&is_leap($yr))
      {
        $MonthLen[2] = 29;
      }
      else
      {
        $MonthLen[2] = 28;
      }
    }
  }
  
  $date = sprintf("%04d-%02d-%02d", $yr, $mo, $dy);
}

print "Finished searching.\n";

sub is_leap {
  # Returns 1 if leap year, 0 if not
  my($yr) = @_;
  
  if ($yr%4)
  {
    0;
  }
  elsif (!($yr%400))
  {
    1;
  }
  elsif ($yr%100)
  {
    1;
  }
  else
  {
    0;
  }
}

Sample places.csv file:

1982-08-26,1983-05-10,40.441164,-79.939020,Freshman Dorm
1983-08-25,1986-05-12,40.452789,-79.948439,Off-Campus Living
2000-02-03,,26.340754,-80.129356,Apartment

Java implementation

This implementation IS FULLY 30W-compliant.

A Java port of the Python implementation can be found from GitHub.

Ruby Geohasher v1.2

This implementation IS FULLY 30W-compliant.

ScottKuma did this as a first excursion into Ruby. Yes, it's long. Yes, it's kinda clunky. However, IT WORKS!

v1.2 adds the ability to use unix-style commandline options in any order.

Any changes, suggestions, etc. are happily accepted!

#!/usr/bin/ruby
# == Synopsis
# geohasher: prints geohash coordinates for a given date & graticule
#
# == Usage
#
# geohasher [OPTION] ... 
# -d, --date YYYY-MM-DD:
#   the date in YYYY-MM-DD or YYYY/MM/DD format), 
#
# -t, --lat x:
#   the latitude "base coordinate"
#
# -g, --long x:
#   the longitude "base coordinate"
#
# -m, --dow x


require 'net/http'
require 'date'
require 'digest'
require 'getoptlong'
require 'rdoc/usage'

def hexFracToDecFrac(hexFracPart)
	#I wish I had a neat little algorithm to do this in one line - but this works!
	#NOTE:  do not feed the preceding "0." to this function....only the fractional part (the part after the decimal point)
	fracLen = hexFracPart.length
	fracPortion = hexFracPart[0..(fracLen-1)]
	fracLen = fracPortion.length
	myLen = (fracLen - 1)
	sum = 0	
	for i in (0 .. myLen)
		numSixteenths = fracPortion[i..i].to_i(16)
		conversionFactor = (16.**(i+1)).to_f
		conversionFactor = 1./conversionFactor
		sum = sum + ((numSixteenths) * conversionFactor)
	end
	return sum.to_s[2..8]
end

# Parse the command line options

opts = GetoptLong.new(
	['--help','-h',GetoptLong::NO_ARGUMENT ],
	['--lat','-t',GetoptLong::REQUIRED_ARGUMENT ],
	['--long','-g',GetoptLong::REQUIRED_ARGUMENT ],
	['--dow','-m',GetoptLong::REQUIRED_ARGUMENT ],
	['--date','-d',GetoptLong::REQUIRED_ARGUMENT ]
)

# Set default items (still parsing...)

myLat = "39"	# Change me to set the desired default graticule's latitude
myLong = "-84"	# Change me to set the desired default graticule's longitude
t=Time.now
myDate = t.strftime("%Y-%m-%d")
dow = ""

begin
opts.each do |opt,arg|
	case opt
		when '--help'
			RDoc::usage
		when '--lat'
			myLat = arg
		when '--long'
			myLong = arg
		when '--dow'
			dow = arg
		when '--date'
			myDate = arg
	end
end
rescue
  RDoc::usage
end


dateSplit = ''
if myDate.split('/').length == 3
	dateSplit = myDate.split('/')
else
	dateSplit = myDate.split('-')
end

myDate = Date.civil(dateSplit[0].to_i, dateSplit[1].to_i, dateSplit[2].to_i)

#fix for the "-30 rule"
fixDate = Date.civil(2008,05,25)
timeDelta = 0
if myLong.to_i > -30 and (myDate > fixDate)
	puts "-30 rule in effect!"
	timeDelta = 1
end

algorithmEncodedDate = myDate.to_s
urlEncodedDate = (myDate - timeDelta).strftime('%Y/%m/%d')

baseURL = 'carabiner.peeron.com'
basePath = '/xkcd/map/data/'
fullPath = basePath + urlEncodedDate
if dow==""
  Net::HTTP.start(baseURL,80) do |http|
    dow = http.get(fullPath).body
  end
end

if !dow.include? "404 Not Found"
	ghash = algorithmEncodedDate+'-'+dow
	digest = Digest::MD5.hexdigest(ghash)
	digest1 = digest[0..15]
	digest2 = digest[16..31]
	puts "(" + myLat + "." + hexFracToDecFrac(digest1) + ", " + myLong + "." + hexFracToDecFrac(digest2) + ")"
else 
	puts "Dow information not available for "+urlEncodedDate
end

macHasher

This implementation IS FULLY 30W-compliant.

macHasher screenshot

Scottkuma worked feverishly to:

1. learn Apple OSX Programming and...
2. put together a geohash calculator for the Mac.

Installation:

It's a normal mac application - drag it to your Applications folder, OR just run it from inside the DMG. I think I compiled it as a Universal Binary. If you can't run it on a particular system and/or version of OSX, please let me know.

Usage:

Start by entering your graticule's Lat/Long numbers. The given numbers are for Cincinnati, Ohio.

For today's graticule, just click "Generate!" For dates in the past (or the near-future, for Saturday & Sunday graticules), select the date on the calendar, then click "Generate!"

Known bugs:

• Requires a valid network connection; locks pretty good when one doesn't exist.
• does not calculate east of -30 correctly for dates prior to 5/27/2008
• window doesn't lock its size like I thought it would...

Planned enhancements:

• will allow for saving of a known "home" location
• will calculate distance & bearing to a known location
• will calculate same for adjacent graticules to find a closer geohash

Geohash for the iPhone

This implementation IS PARTIALLY 30W-compliant.

Geohash screenshot

Geohash for the iPhone is available here in the app store (for free).

The new version of Geohash now supports looking forward over the weekend. Yay!

The app is partially 30W compliant. It produces the correct coordinates, but doesn't allow you to select tomorrow's date (during the week) or Monday (from Friday afternoon onward).

Next feature up? The most requested feature by far is the ability to view Geohash locations in surrounding graticules.

I'll also be publishing the source code when I get a chance. (Update: I'm still a little unsure about the implications of Apple's NDA on their SDK. I'm trying to determine if releasing the source violates the NDA or not. It'll be out for sure once I make sure I won't get spanked by Apple!)

Thanks to Scottkuma for a spot of help with the MD5 hash conversion.

PS. Obviously, feel free to leave reviews on the app store telling everyone what you think, good and bad, but also send feedback to me (casey@kckd.org), so I can respond directly!

Small Hash Inquiry Tool

This implementation IS FULLY 30W-compliant.

Small Hash Inquiry Tool is an online tool Ekorren built to his own needs but later rebuilt to be globally usable.

Compared to the nifty tools like those for the iPhone, this one looks ugly to the end. Which was intended as it should be stripped from all colourful overhead, featuring just basic compressed information, all on one page and from everywhere.

Features:

• lists up to nine nearby hashpoints per day, today and upcoming (no retro)
• may be called from a bookmark without needing further input
• calculates approximate distance and direction
• shows the location on configurable maps on request
• includes the globalhash
• does it all at once, and
• is so much basic that it works from virtually every phone which isn't entirely incapable of browsing.

Usage information is available from it's own page.

Probability Calculators

These do not calculate the hash, but instead the probability of the hashpoint to land in certain areas.

• Land usage - calculates the probability of certain types of land (forests, water, and the like).
• Public transport probability - calculates the probability of a certain distance from public transport.

Geohash Droid (for Android phones)

This implementation IS FULLY 30W-compliant.

Scan to find the app in the Market

Geohash Droid, a small, (so far) simple little Geohashing app for Android phones, can be found in the Android Marketplace as a free app. So far, it gets the stock and hash values, plots it out, and follows you as you get closer to it. It also has wiki-updating features (not since recaptcha was installed) and can automatically figure out what graticule has the closest point to where you are. Simple, effective. There's more stuff planned, but that's later.

The project itself is hosted on Google Code. The most recent version (as per this writing) is 0.7.10. If you go from the Marketplace (far easier), feel free to leave reviews and such. If you have something specific to say, either file an issue at the Google Code site, hit the group page, or email me.

So hey, give it a shot! What've you got to lose? Enjoy!

The Tablet of Adventure (Geohash for Nokia N900)

This implementation IS FULLY 30W-compliant.

The Tablet of Adventure is a social adventure gaming tool that supports geohashes. It is available for Maemo 5 (Nokia N900) from Maemo Extras.

With TToA you can seek geohashes in your area or create your own collaborative adventures and share them via Qaiku.

Source code is available from GitHub.

Automatic Daily Notifications

After registering, it will automatically notify users about all hashpoints as soon as they become available. Graticules are divided into 100 sub-graticules to allow users to only be notified when a hashpoint is near home, or alternatively, for all accessible hashpoints in a graticule. For more information, see the program's page.

Geohash module for phenny IRC bot

This implementation IS FULLY 30W-compliant.

This page describes the geohashing module of the Phenny IRC bot, which currently runs as user "Shmulik" or "geolik" on the #geohashing IRC channel.

• He can provide you with geohashing related information lookups.
• He notifies the channel of important recent changes.

He understands the following commands:

.# [location [date]] 
returns the geohash (or globalhash) for the given place and date, and a location .lookup for this place. 
Parameters in square brackets are optional. This method is also triggered by the publication of new 
coordinates by zbot, supplementing its information with the matching globalhashes.
location: A string describing a graticule or populated place, or the string "global" for globalhashes. 
It will try to identify the name using the list of all graticules, and http://geonames.org. 
Defaults to the current globalhash if omitted. If the location name contains spaces, replace these by a '+'
date: A date in the ISO format yyyy-mm-dd. Defaults to a current date (for some time zones) if omitted.

.where's location|username
1) returns the corresponding graticule name and coordinates for the given search term. 
2) If the location is not found in the graticule database, it will try to find a user of that name. If the 
user has registered in location categories (for example with Template:asg) it will display the location(s)
where the user is "at home".
3) finally, if both fails, it may suggest places from the geonames database and provide their coordinates.

location: A pair of coordinates, separated with a space and/or a comma. Alternatively, the name of a 
graticule. Alternatively, the name of any populated place. 

.lookup lat,lon
returns a human readable, hierarchical identification of the given coordinates. The output may vary, 
from a mere country code to street-level details, depending on the available information.
lat,lon: The latitude and longitude of a location, separated by a space and/or a comma.

.rcwatch
Runs the RecentChanges watch daemon, if it is not running already. You should not need this, unless it 
has been stopped before.

.stopwatch
Sets a flag that stops the RecentChanges watch daemon before its next update cycle. Do not use, unless 
in case of wiki spam proliferating into the update messages. 

.addwatch tag=regex
Adds a new regular expression to the notification list. If the title, comment, or author of a recent change 
match the regular expression, a notification labeled with "tag" will be sent to the IRC channel. This 
command only works in public channels.

.watchlist
Displays the current list of notifications, and their numbers. This command should be used in a private 
message preferably, as it will return the whole list.

.rmwatch number
Removes a notification from the watchlist. Number is the rule index provided by the .watchlist command.

Examples

relet: .# San+Francisco 2008-05-22
Shmulik: Geohash for San Francisco, United States on 2008-05-22 is: 37.972874275358, -122.238696518558. http://geohash.org/9qc042u2pbvd
Shmulik: Location: Alhambra Valley Rd, Contra Costa, California, US - distance: 0.11km.

relet: .where's Paris
Shmulik: There's Paris, Texas at 33,-95. http://geohashing.org/33,-95
Shmulik: There's Paris, France at 48,2. http://geohashing.org/48,2

relet: .lookup 52.5785927440891,13.8874053955078
Shmulik: Location: Earth, Europe, Germany, Brandenburg, Strausberg.

relet: .addwatch A new report on Main Page?=Template:Expedition Images/
Shmulik: Notification installed. tag 'A new report on Main Page?' = pattern 'Template:Expedition Images/'

Shmulik: New page: File talk:2010011233-81LM02.JPG was created by Reinhard. (65+x)

The code for this module is available in the python geohashing toolshed at http://relet.net/trac/pygeohashing - it has various dependencies though.

Other, less geohashing or wiki related commands

.weather location
The commands .weather, .now, .3day and .7day all show weather reports for various time spans for a given location

.seen person
Tells you when person was last seen saying something in the IRC channel

Shmulik, tell person ...
Stores a message which will be displayed to "person" as soon as they say something in the IRC channel.

.grab [user]
Puts the last line said [by that user] into the quote archive. 

.quote [user]
Recalls a random quote [by that user].

Active Geohasher

This implementation IS FULLY 30W-compliant.

Active geohasher is a web application by Sermoa which provides resources for geohashers. You can subscribe to graticules to receive a daily email containing the address, distance from your home location, and useful links. It also tells you the globalhash.

The site provides graticule integration with twitter, flickr and youtube. A google earth feed is provided per gratiucule. Every geohash has a page showing various google maps, useful links and a PDF poster which you can download and print to take to the geohash.

Active geohasher is open source (written in Ruby on Rails). Please contribute if you have ideas or would like to translate it into a different language. There is also a twitter account that delivers news and direct message geohashing notifications: @activegeohasher

JSON Web Service

This implementation IS FULLY 30W-compliant.

A geohashing JSON web service is available at: http://relet.net/geo/[lat]/[lon]/[YYYY-mm-dd] (example) The output will contain the following values in a dictionary:

• error - if an error occurred retrieving the data - example: "DJIA for 2011-12-24 not available yet."
• exception - if an error occurred parsing the input or calculating the output - example: "time data '2011-13-24' does not match format '%Y-%m-%d'"

or:

• djia - DJIA as retrieved from geo.crox
• lat - latitude of the geohash
• lon - longitude of the geohash
• graticule - name of the graticule (may be null)
• global-lat - latitude of the globalhash
• global-lon - longitude of the globalhash
• ... - additional data may be present in the reply. This service may be extended in the future.

Geco

This implementation IS FULLY 30W-compliant.

A re-implementation of the official map using leaflet/cloudmade and the above web service. By using geo.crox as a data source, it is hopefully more reliable than the official map.

http://relet.net/geco

Parameters:

• lat - latitude of the initial graticule
• lon - longitude of the initial graticule
• zoom - initial zoom level
• date - initial date in YYYY-MM-DD format

e.g: http://relet.net/geco/?date=2005-05-26&lat=37&lon=-122&zoom=8

HashPlacer

The HashPlacer is a perl script that allows you to define limit boxes on a map, and will notify you via email if the day's geohash point lands in one of these boxes. This is especially useful if you define a limit box surrounding your favorite park, or your neighborhood, or even your couch. Currently the only areas supported are "boxes"... two latitude points and two longitude points define the corners of a graticule-shaped "box".

User:AeroIllini/HashPlacer