diff --git a/lib/xmet/hodograph.py b/lib/xmet/hodograph.py
index 68baa90..c90e0c2 100644
--- a/lib/xmet/hodograph.py
+++ b/lib/xmet/hodograph.py
@@ -18,6 +18,9 @@ def radians(degrees: float) -> float:
 def degrees(radians: float) -> float:
     return (radians * (180.0 / math.pi)) - 90
 
+def knots(ms: float) -> float:
+    return ms * 1.944
+
 class Hodograph():
     def __init__(self, width, height):
         self.width  = min(width, height)
@@ -151,7 +154,8 @@ class Hodograph():
                 if sx_last is not None and sy_last is not None:
                     cr.move_to(x + sx_last, x + sy_last)
 
-            sx, sy = self.sample_to_screen(sample.wind_speed, sample.wind_dir)
+            sx, sy = self.sample_to_screen(knots(sample.wind_speed),
+                                           sample.wind_dir)
 
             if first:
                 cr.move_to(x + sx, y + sy)