Merge pull request #11 from geocrystal/use-geo_bearing_shard

use Geo::Bearing

shard.yml

@@ -11,6 +11,8 @@ dependencies:
     version: ">= 0.6.0"
   geohash:
     github: geocrystal/geohash
+  geo_bearing:
+    github: geocrystal/geo_bearing
 
 development_dependencies:
   ameba:

src/geo.cr

@@ -1,5 +1,6 @@
 require "convex_hull"
 require "geohash"
+require "geo_bearing"
 require "./geo/utils"
 require "./geo/coord"
 require "./geo/polygon"

src/geo/bearing.cr

@@ -1,35 +1,8 @@
 module Geo
   struct Coord
-    # The formula used for calculating the initial bearing between two points on the Earth's surfaceis
-    # is derived from the broader concepts of great-circle distance and navigation on a spherical Earth model.
-    # https://en.wikipedia.org/wiki/Great-circle_distance
-    #
-    # https://github.com/Turfjs/turf/blob/master/packages/turf-bearing/index.ts
+    # Calculates initial and final bearings between two points using great-circle distance formulas
     def bearing(to : Geo::Coord, final = false) : Float64
-      if final
-        # Calculate the bearing from the destination point back to the original point
-        reverse_bearing = calculate_bearing(to.lat, to.lng, lat, lng)
-
-        # Adjust by 180 degrees to get the final bearing in the correct direction
-        (reverse_bearing + 180) % 360
-      else
-        calculate_bearing(lat, lng, to.lat, to.lng)
-      end
-    end
-
-    private def calculate_bearing(lat1, lng1, lat2, lng2) : Float64
-      rad_lat1 = Geo::Utils.degrees_to_radians(lat1)
-      rad_lng1 = Geo::Utils.degrees_to_radians(lng1)
-      rad_lat2 = Geo::Utils.degrees_to_radians(lat2)
-      rad_lng2 = Geo::Utils.degrees_to_radians(lng2)
-
-      delta_lng = rad_lng2 - rad_lng1
-
-      a = Math.sin(delta_lng) * Math.cos(rad_lat2)
-      b = Math.cos(rad_lat1) * Math.sin(rad_lat2) -
-          Math.sin(rad_lat1) * Math.cos(rad_lat2) * Math.cos(delta_lng)
-
-      Geo::Utils.radians_to_degrees(Math.atan2(a, b)) % 360
+      Geo::Bearing.bearing(lat, lng, to.lat, to.lng, final)
     end
   end
 end

src/geo/utils.cr

@@ -21,13 +21,5 @@ module Geo
       return 0 if val == 0 # colinear
       val > 0 ? 1 : 2      # clockwise or counterclockwise
     end
-
-    def degrees_to_radians(degrees : Number) : Float64
-      degrees * Math::PI / 180.0
-    end
-
-    def radians_to_degrees(radians : Number) : Float64
-      radians * 180.0 / Math::PI
-    end
   end
 end