lib/geo_swap/zone.rb in geo_swap-0.0.2 vs lib/geo_swap/zone.rb in geo_swap-0.1.0

@@ -1,8 +1,9 @@
 module GeoSwap
   class Zone
-    def initialize(longitude)
+    def initialize(latitude, longitude)
+      @latitude = latitude
       @longitude = longitude.to_f
     end
 
     def number
       @number ||= begin
@@ -12,8 +13,35 @@
       end
     end
 
     def origin
       @origin ||= ((number - 1) * 6) - 177
+    end
+
+    def letter
+      case @latitude
+      when 72..84   then 'X'
+      when 64...72  then 'W'
+      when 56...64  then 'V'
+      when 48...56  then 'U'
+      when 40...48  then 'T'
+      when 32...40  then 'S'
+      when 24...32  then 'R'
+      when 16...24  then 'Q'
+      when 8...16   then 'P'
+      when 0...8    then 'N'
+      when -8...0   then 'M'
+      when -16...-8 then 'L'
+      when -24...-16 then 'K'
+      when -32...-24 then 'J'
+      when -40...-32 then 'H'
+      when -48...-40 then 'G'
+      when -56...-48 then 'F'
+      when -64...-56 then 'E'
+      when -72...-64 then 'D'
+      when -80...-72 then 'C'
+      else
+        'Z'
+      end
     end
   end
 end