diff --git a/lib/xmet/hodograph.py b/lib/xmet/hodograph.py
index cbf4176..86504ae 100644
--- a/lib/xmet/hodograph.py
+++ b/lib/xmet/hodograph.py
@@ -25,12 +25,15 @@ class Hodograph():
         self.height = min(width, height)
         self.radius = min(width, height) * 1.2
 
+        self.offset_width  = 0.1
+        self.offset_height = 0.9
+
     def sample_to_screen(self, wind_speed: dir, wind_dir: float) -> tuple:
         r = self.radius * min(wind_speed, WIND_SPEED_MAX) / WIND_SPEED_MAX
 
         return (
-            0.1 * self.width  + r * math.cos(radians(wind_dir)),
-            0.9 * self.height + r * math.sin(radians(wind_dir))
+            self.offset_width  * self.width  + r * math.cos(radians(wind_dir)),
+            self.offset_height * self.height + r * math.sin(radians(wind_dir))
         )
 
     def draw_speed_lines(self, cr: cairo.Context, x, y):
@@ -41,8 +44,8 @@ class Hodograph():
         cr.set_dash([5, 5], 1)
 
         for speed in range(WIND_SPEED_MIN, WIND_SPEED_MAX+1, WIND_SPEED_STEP):
-            cr.arc(x + 0.1 * self.width,
-                   y + 0.9 * self.height,
+            cr.arc(x + self.offset_width  * self.width,
+                   y + self.offset_height * self.height,
                    self.radius * min(speed, WIND_SPEED_MAX) / WIND_SPEED_MAX,
                    0,
                    2*math.pi)