util.rb

# -*- coding: utf-8 -*-

class Util

  def self.deg2rad(degree)
    degree * Math::PI / 180.0
  end

  # ヒュベニの距離計算式 単位: m
  def self.geo_distance(geo_a, geo_b)
    lat_ave  = deg2rad((geo_a[:lat] + geo_b[:lat]) / 2.0)
    lat_diff = deg2rad(geo_a[:lat] - geo_b[:lat])
    lon_diff = deg2rad(geo_a[:lon] - geo_b[:lon])

    m = 6335439.327 / Math.sqrt((1.0 - 0.00669438 * Math.sin(lat_ave) ** 2) ** 3)
    n = 6378137.0 / Math.sqrt(1.0 - 0.00669438 * Math.sin(lat_ave) * 2)

    Math.sqrt((m * lat_diff) ** 2 + (n * Math.cos(lat_ave) * lon_diff) ** 2)
  end

end