Class: Graticule::Distance::Haversine

Inherits:
DistanceFormula show all
Defined in:
lib/graticule/distance/haversine.rb

Overview

The Haversine Formula works better at small distances than the Spherical Law of Cosines

Thanks to Chris Veness (www.movable-type.co.uk/scripts/LatLong.html) for distance formulas.

Class Method Summary collapse

Methods inherited from DistanceFormula

#initialize

Constructor Details

This class inherits a constructor from Graticule::Distance::DistanceFormula

Class Method Details

.distance(from, to, units = :miles) ⇒ Object

Calculate the distance between two Locations using the Haversine formula

Graticule::Distance::Haversine.distance(
  Graticule::Location.new(:latitude => 42.7654, :longitude => -86.1085),
  Graticule::Location.new(:latitude => 41.849838, :longitude => -87.648193)
)
#=> 101.061720831836



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# File 'lib/graticule/distance/haversine.rb', line 19

def self.distance(from, to, units = :miles)
  from_longitude  = from.longitude.to_radians
  from_latitude   = from.latitude.to_radians
  to_longitude    = to.longitude.to_radians
  to_latitude     = to.latitude.to_radians

  latitude_delta  = to_latitude - from_latitude
  longitude_delta = to_longitude - from_longitude

  a = sin(latitude_delta/2)**2 + 
      cos(from_latitude) * 
      cos(to_latitude) * 
      sin(longitude_delta/2)**2

  c = 2 * atan2(sqrt(a), sqrt(1-a))

  d = EARTH_RADIUS[units.to_sym] * c
end