Scale graph to maximum 100 knots plotted

lib/xmet/hodograph.py

@@ -4,7 +4,7 @@ import cairo
 from xmet.igra     import IGRAReader
 from xmet.sounding import Sounding
 
-WIND_SPEED_MAX  = 100 # knots
+WIND_SPEED_MAX  = 140 # knots
 WIND_SPEED_MIN  =  10
 WIND_SPEED_STEP =  10
 
@@ -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)