Module: GeoCalc::Bearing

Defined in:
lib/geo_calc/calc/bearing.rb

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.bearing_to(base_point, point) ⇒ Numeric

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

Parameters:

  • Latitude/longitude (GeoPoint) —

    of destination point

Returns:

  • (Numeric) —

    initial bearing in degrees from North



15
16
17
18
19
20
21
22
23
24
25
 
# 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) ⇒ Numeric

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

Parameters:

  • Latitude/longitude (GeoPoint) —

    of destination point

Returns:

  • (Numeric) —

    final bearing in degrees from North



38
39
40
41
42
43
44
45
46
47
48
49
50
 
# 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

Instance Method Details

#bearing_to(point) ⇒ Object 



4
5
6
 
# File 'lib/geo_calc/calc/bearing.rb', line 4

def bearing_to point
  GeoCalc::Bearing.bearing_to self, point
end

#final_bearing_to(point) ⇒ Object 



27
28
29
 
# File 'lib/geo_calc/calc/bearing.rb', line 27

def final_bearing_to point
  GeoCalc::Bearing.final_bearing_to self, point
end