Module: Haversine

Defined in:
lib/haversine.rb,
lib/haversine/distance.rb

Defined Under Namespace

Classes: Distance

Constant Summary collapse

RAD_PER_DEG = 
Math::PI / 180

Class Method Summary collapse

Class Method Details

.calc(dlat, lat1, lat2, dlon) ⇒ Object

TODO How can this be more descriptively named?



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# File 'lib/haversine.rb', line 38

def self.calc(dlat, lat1, lat2, dlon)
  (Math.sin(rpd(dlat)/2))**2 + Math.cos(rpd(lat1)) * Math.cos((rpd(lat2))) * (Math.sin(rpd(dlon)/2))**2
end

.distance(lat1, lon1, lat2 = nil, lon2 = nil) ⇒ Object

given two lat/lon points, compute the distance between the two points using the haversine formula



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

def self.distance(lat1, lon1, lat2=nil, lon2=nil)
  # Accept two arrays of points in addition to four coordinates
  if lat1.is_a?(Array) && lon1.is_a?(Array)
    lat2, lon2 = lon1
    lat1, lon1 = lat1
  elsif lat2.nil? || lon2.nil?
    raise ArgumentError
  end

  dlon = lon2 - lon1
  dlat = lat2 - lat1

  a = calc(dlat, lat1, lat2, dlon)
  c = 2 * Math.atan2( Math.sqrt(a), Math.sqrt(1-a))

  Haversine::Distance.new(c)
end

.rpd(num) ⇒ Object

Radians per degree



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# File 'lib/haversine.rb', line 43

def self.rpd(num)
  num * RAD_PER_DEG
end