@@ -1,4 +1,19 @@
+require "delegate"
+
 module GeoRecord
+  # Ensure that when coordinates are printed that they are always in decimal degrees,
+  # and not e.g. 4.0e-05
+  # Unfortunately you can't extend Numeric classes directly (e.g. `Coord < Float`).
+  class Coord < DelegateClass(Float)
+    def initialize(obj)
+      super(obj)
+    end
+
+    def to_s
+      format("%.7f", self)
+    end
+  end
+
   # This scaling factor is used to convert between the float lat/lon that is
   # returned by the API, and the integer lat/lon equivalent that is stored in
   # the database.
module GeoRecord
  # This scaling factor is used to convert between the float lat/lon that is
  # returned by the API, and the integer lat/lon equivalent that is stored in
  # the database.
  SCALE = 10000000

  def self.included(base)
    base.scope :bbox, ->(bbox) { base.where(OSM.sql_for_area(bbox)) }
    base.before_save :update_tile
  end

  # Is this node within -90 >= latitude >= 90 and -180 >= longitude >= 180
  # * returns true/false
  def in_world?
    return false if lat < -90 || lat > 90
    return false if lon < -180 || lon > 180
    true
  end

  def update_tile
    self.tile = QuadTile.tile_for_point(lat, lon)
  end

  def lat=(l)
    self.latitude = (l * SCALE).round
  end

  def lon=(l)
    self.longitude = (l * SCALE).round
  end

  # Return WGS84 latitude
  def lat
    latitude.to_f / SCALE
  end

  # Return WGS84 longitude
  def lon
    longitude.to_f / SCALE
  end
end

What's the benefit of using delegation here over just inheriting from `Float` and overriding the `to_s` method? If we did that then I think we wouldn't need to special case the AMF encoding (because Coord would match Numeric) and we wouldn't need `to_f` on the pack etc?