Haversine - Straight Line Distance Between Two Sets of Geographical Coordinates (Latitude, Longitude)

haversine.rb

# radius of earth in meters
R = 6371000;

def haversine(coord1:, coord2:)
  # first add our own radians function since Ruby Math does not have one
  radians = -> (degrees) { degrees * (Math::PI / 180)}

  # convert latitude degrees to radians
  phi_1 = radians.call(coord1[:latitude]);
  phi_2 = radians.call(coord2[:latitude]);

  # delta being the "difference" between the latitudes and longitudes of each coordinate set expressed
  # in radians
  delta_phi = radians.call(coord2[:latitude] - coord1[:latitude]);
  delta_lambda = radians.call(coord2[:longitude] - coord1[:longitude]);

  # sin²(φB - φA/2) + cos φA * cos φB * sin²(λB - λA/2)
  a = Math.sin(delta_phi/2.0)**2 + Math.cos(phi_1) * Math.cos(phi_2) * Math.sin(delta_lambda/2.0)**2;

  # 2 * atan2( √a, √(1−a) )
  c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));

  meters = R * c;
  kilometers = meters / 1000.0;
  miles = kilometers / 1.609344;

  { meters: meters, kilometers: kilometers, miles: miles }
end