lib/swissgrid/ch1903.rb in swissgrid-0.1.0 vs lib/swissgrid/ch1903.rb in swissgrid-0.1.1

@@ -1,66 +1,96 @@
 module Swissgrid
 
-  module Ch1903
+  module CH1903
 
-    PHI_BERN = 169028.66
-    LAMBDA_BERN = 26782.5
-    SCALE = 10000
+    # Projection centre Bern
+    PHI_BERN = 169_028.66 # in meters
+    LAMBDA_BERN = 26_782.5 # in meters
+    SCALE = 10_000 # scale to unit 10000"
 
+
+    # Converts a CH1903 point to a WGS84 point.
+    #
+    # @param a_point [List] the CH1903 point to be converted.
+    # @return [List] the converted CH1903 point as WGS84 point.
+    #
     def self.from_wgs84(a_point)
       lat, lon, z = a_point
-      phi_sec = to_sexagesimal(lat)
-      lambda_sec = to_sexagesimal(lon)
+      phi_sec = to_arc_seconds(lat)
+      lambda_sec = to_arc_seconds(lon)
       lambda_prime = (lambda_sec - LAMBDA_BERN) / SCALE.to_f
       phi_prime = (phi_sec - PHI_BERN) / SCALE.to_f
+
+      # compute WGS84 point
       convert(lambda_prime, phi_prime, z)
     end
 
+
     private
 
+
+    # Computes the WGS84 point by means of the auxiliary parameters lambda', phi' and height h.
+    #
+    # @param lambda_prime [Float] auxiliary parameter lambda'.
+    # @param phi_prime [Float] auxiliary parameter phi'.
+    # @param h [Float] height h.
+    #
     def self.convert(lambda_prime, phi_prime, h)
       y = [
-          600072.37,
-          211455.93 * lambda_prime,
-          -10938.51 * lambda_prime * phi_prime,
+          600_072.37,
+          211_455.93 * lambda_prime,
+          -10_938.51 * lambda_prime * phi_prime,
           -0.36 * lambda_prime * (phi_prime ** 2),
           -44.54 * (lambda_prime ** 3)
       ].reduce(:+)
 
       x = [
-          200147.07,
-          308807.95 * phi_prime,
-          3745.25 * (lambda_prime ** 2),
+          200_147.07,
+          308_807.95 * phi_prime,
+          3_745.25 * (lambda_prime ** 2),
           76.63 * (phi_prime ** 2),
           -194.56 * (lambda_prime ** 2) * phi_prime,
           119.79 * (phi_prime ** 3)
       ].reduce(:+)
 
-      z = if h.nil?
+      z = if h.nil? # if nil do nothing
             h
           else
             [
                 h - 49.55,
                 2.73 * lambda_prime,
                 6.94 * phi_prime
             ].reduce(:+)
           end
 
-      z.nil? ? [y, x] : [y, x, z]
+      z.nil? ? [y, x] : [y, x, z] # if z is nil, remove z component
     end
 
 
-    def self.to_gps_triple(dec_degress)
-      degrees = dec_degress.to_i
-      minutes = (60*(dec_degress - degrees)).to_i
-      seconds = (60*(dec_degress - degrees) - minutes) * 60
+    # Converts decimal degrees to a DMS triple that consists of the parts degree, minutes and seconds.
+    #
+    # @param dec_degrees [Float] decimal degrees to be converted.
+    # @return [List] a triple [degree, minutes, seconds].
+    #
+    def self.to_dms_triple(dec_degrees)
+      degrees = dec_degrees.to_i
+      minutes = (60*(dec_degrees - degrees)).to_i
+      seconds = (60*(dec_degrees - degrees) - minutes) * 60
       [degrees, minutes, seconds]
     end
 
-    def self.to_sexagesimal(dec_degress)
-      degree, minutes, seconds = to_gps_triple(dec_degress)
+
+    # Converts decimal degrees to arc seconds.
+    #
+    # @param dec_degrees [Float] decimal degrees to be converted.
+    # @return [Float] arc seconds.
+    #
+    def self.to_arc_seconds(dec_degrees)
+      degree, minutes, seconds = to_dms_triple(dec_degrees)
       degree * 3600 + minutes * 60 + seconds
     end
 
   end
+
+  Ch1903 = CH1903 # to be compatible to previous versions
 
 end
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