h1. Haversine Distance

This gem calculates the Haversine distance between two points given their longitude and latitude. This is done using trigonometry without ActiveRecord or SQL. See http://en.wikipedia.org/wiki/Haversine_formula for details on the Haversine formula.

This is a replacement for all geo libraries that use built-in SQL DB functionality for their calculations.

h2. Install & Usage

Install this gem with @gem install haversine@. Calling @Haversine.distance@ with four lat/lon coordinates returns a @Haversine::Distance@ object which can provide output in kilometers, meters, miles, or feet.

<pre>
require 'haversine'

distance = Haversine.distance(35.61488, 139.5813, 48.85341, 2.3488)

distance.class => Haversine::Distance
distance.to_miles => 6032.71091869803
distance.to_kilometers => 9715.47049115903
distance.to_meters => 9715470.49115903
distance.to_feet => 31852713.6507256
</pre>

Convenience aliases for the measurements exist:
<pre>
distance.to_kilometers == distance.to_km
distance.to_meters == distance.to_m
distance.to_miles == distance.to_mi
distance.to_feet == distance.to_ft
</pre>

Note that @to_m@ is the distance in meters, not miles.

  puts "#{dist[:feet]}"
  puts "#{dist.meters}"
  puts "#{dist[:km]}"
  puts "#{dist[:miles]}"
  puts "#{dist.to_mi}"
  puts "#{dist.to_miles_}"
  dist[:km].to_s.should match(/7\.376*/)
  dist.to_km.to_s.should match(/7\.376*/)  
end  

If you have lat/lon pairs stored in an array, you can alternately provide two arrays when calling @Haversine.distance@:

<pre>
require 'haversine'
new_york_city = [40.71427, -74.00597]
santiago_chile = [-33.42628, -70.56656]
Haversine.distance(new_york_city, santiago_chile).to_miles => 5123.73
</pre>

Note: Haversine is used in the "geo_magic":https://github.com/kristianmandrup/geo_magic gem

h2. Contributing to haversine
 
* Check out the latest master to make sure the feature hasn't been implemented or the bug hasn't been fixed yet
* Check out the issue tracker to make sure someone already hasn't requested it and/or contributed it
* Fork the project
* Start a feature/bugfix branch
* Commit and push until you are happy with your contribution
* Make sure to add tests for it. This is important so I don't break it in a future version unintentionally.
* Please try not to mess with the Rakefile, version, or history. If you want to have your own version, or is otherwise necessary, that is fine, but please isolate to its own commit so I can cherry-pick around it.

h2. Copyright

Copyright (c) 2011 Kristian Mandrup. See LICENSE.txt for
further details.