module GeoCalc::Bearing

Public Class Methods

bearing_to(base_point, point) click to toggle source

Returns the (initial) bearing from this point to the supplied point, in degrees see(#williams.best.vwh.net/avform.htm#Crs)

@param [GeoPoint] Latitude/longitude of destination point

@return [Numeric] initial bearing in degrees from North

# File lib/geo_calc/calc/bearing.rb, line 15
def self.bearing_to base_point, point
  lat1 = base_point.lat.to_rad
  lat2 = point.lat.to_rad
  dlon = (point.lon - base_point.lon).to_rad

  y = Math.sin(dlon) * Math.cos(lat2)
  x = Math.cos(lat1) * Math.sin(lat2) - Math.sin(lat1) * Math.cos(lat2) * Math.cos(dlon)
  bearing = Math.atan2(y, x)

  (bearing.to_deg + 360) % 360
end
final_bearing_to(base_point, point) click to toggle source

Returns final bearing arriving at supplied destination point from this point; the final bearing will differ from the initial bearing by varying degrees according to distance and latitude

@param [GeoPoint] Latitude/longitude of destination point

@return [Numeric] final bearing in degrees from North

# File lib/geo_calc/calc/bearing.rb, line 38
def self.final_bearing_to base_point, point
  # get initial bearing from supplied point back to this point...
  lat1 = point.lat.to_rad
  lat2 = base_point.lat.to_rad
  dlon = (base_point.lon - point.lon).to_rad

  y = Math.sin(dlon) * Math.cos(lat2)
  x = Math.cos(lat1)*Math.sin(lat2) - Math.sin(lat1)*Math.cos(lat2)*Math.cos(dlon)
  bearing = Math.atan2(y, x)

  # ... & reverse it by adding 180°
  (bearing.to_deg+180) % 360
end

Public Instance Methods

bearing_to(point) click to toggle source

@returns [Numeric] bearing in degrees

# File lib/geo_calc/calc/bearing.rb, line 4
def bearing_to point
  GeoCalc::Bearing.bearing_to self, point
end
final_bearing_to(point) click to toggle source
# File lib/geo_calc/calc/bearing.rb, line 27
def final_bearing_to point
  GeoCalc::Bearing.final_bearing_to self, point
end