Contents

module GeoCalc::Calc
  module Destination
    def destination_point brng, dist
      GeoCalc::Calc::Destination.destination_point self, brng, dist
    end

    # Returns the destination point from this point having travelled the given distance (in km) on the 
    # given initial bearing (bearing may vary before destination is reached)
    # 
    #   see http:#williams.best.vwh.net/avform.htm#LL
    # 
    # - Numeric bearing: Initial bearing in degrees
    # - Numeric dist: Distance in km
    # Returns GeoPoint: Destination point

    def self.destination_point base_point, brng, dist
      dist = dist / base_point.earth_radius_km  # convert dist to angular distance in radians
      brng = brng.to_rad 
      lat1 = base_point.lat.to_rad
      lon1 = base_point.lon.to_rad

      lat2 = Math.asin( Math.sin(lat1) * Math.cos(dist) + Math.cos(lat1) * Math.sin(dist) * Math.cos(brng) )
      lon2 = lon1 + Math.atan2(Math.sin(brng) * Math.sin(dist) * Math.cos(lat1), Math.cos(dist) - Math.sin(lat1) * Math.sin(lat2))

      lon2 = (lon2 + 3*Math::PI) % (2*Math::PI) - Math::PI  # normalise to -180...+180   

      GeoPoint.new lat2.to_deg, lon2.to_deg
    end
  end
end

Version data entries

1 entries across 1 versions & 1 rubygems

Version	Path
geo_calc-0.7.1	lib/geo_calc/calc/destination.rb