Contents

require "geographiclib"

module GeoRb
  class Distance
    EARTH_RADIUS = 6_371.0088

    attr_reader :kilometers
    alias_method :km, :kilometers

    def initialize(*locations)
      @kilometers = case locations.size
      when 1
        Float(locations.first) if locations.size == 1
      else
        locations.each_cons(2).reduce(0) do |distance, pair|
          a, b = sanitize_location(pair.first), sanitize_location(pair.last)
          distance + measure(a, b)
        end
      end
    end

    def ensure_same_altitude(a, b)
      raise LatitudeMismatch if (a.altitude - b.altitude).abs > 1e-6
    end

    def measure(a, b)
      ensure_same_altitude(a, b)
      r = GeographicLib::Geodesic::WGS84.inverse(a.latitude, a.longitude, b.latitude, b.longitude)
      r[:s12] / 1_000
    end

    private

    def sanitize_location(location)
      case location
      when Location, Point
        location
      when Array
        case location.size
        when 2..3
          Point.new(*location.map(&:to_f))
        else
          raise CoordsError
        end
      when String
        points = location.split(",")
        raise CoordsError unless [2, 3].include?(points.size)

        Point.new(*points.map(&:to_f))
      else
        raise LocationError
      end
    end
  end

  class LatitudeMismatch < ArgumentError
    def message
      "Calculating distance between points with different altitudes is not supported"
    end
  end

  class LocationError < ArgumentError
    def message
      "Invalid locations"
    end
  end

  class CoordsError < ArgumentError
    def message
      "In order to calculate the distance between points it is necessary to have at least latitude and longitude"
    end
  end
end

Version data entries

1 entries across 1 versions & 1 rubygems

Version	Path
geo_rb-0.0.1	lib/geo_rb/distance.rb