NOTE: this is not maintained. Recommend checking out other gems such as this one:
https://rubygems.org/gems/dynamodb_geo

---
= geohash

* http://rubyforge.org/projects/geohash

== DESCRIPTION:

GeoHash Gem for Ruby (c) 2008-2010 David Troy
[email protected]

Geohash is a latitude/longitude encoding system invented by Gustavo Niemeyer when writing the
web service at geohash.org, and put into the public domain. Geohashes offer properties like
arbitrary precision, similar prefixes for nearby positions, and the possibility of gradually
removing characters from the end of the code to reduce its size (and gradually lose precision).

See these resources online:
http://geohash.org
http://en.wikipedia.org/wiki/Geohash
http://openlocation.org/geohash/geohash-js (javascript implementation and demo)

== FEATURES/PROBLEMS:

* Encode to Geohash Format to an arbitrary level of precision
* Decode from Geohash Format to an arbitrary level of precision
* C implementation is over 10 times faster than native Ruby code (we checked)
* No known problems

== SYNOPSIS:

GeoHash is very easy to use (and fast) because it's written in C with Ruby bindings.

  require 'rubygems'
  require 'geohash'

  GeoHash.decode('f77')
  => [63.98438, -73.82813]

  GeoHash.encode(39.51, -76.24)
  => "dr1bc0edrj"
  
  # Decode a geohash to a bounding box
  decode_bbox('dqcw4')
  => [39.0234375, -76.552734375], [39.0673828125, -76.5087890625]]
  
You can encode or decode to an arbitrary level of precision:

# Encode latitude and longitude to a geohash with precision digits
encode(lat, lon, precision=10)

# Decode a geohash to a latitude and longitude with decimals digits
decode(geohash, decimals=5)

Have fun with this!  GeoHash is the new black.

== REQUIREMENTS:

* GCC and a Gnu-ish build environment (for native extensions)

== INSTALLATION

1) Enable gems from github, if you haven't already done so (rubygems >= 1.2):
    > sudo gem sources -a http://gems.github.com

2) Install gem
    > sudo gem install davetroy-geohash

3) Profit!

== LICENSE:

(The MIT License)

Copyright (c) 2008-2010 David Troy

Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
'Software'), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.