From df8988183dafe648d0fcf57b93cb5be26f051354 Mon Sep 17 00:00:00 2001
From: Tom Payne <twpayne@gmail.com>
Date: Mon, 22 Sep 2008 20:56:26 +0200
Subject: [PATCH] Fix initial_bearing_to and add rad_to_compass.

---
 igc2kmz/coord.py | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/igc2kmz/coord.py b/igc2kmz/coord.py
index 4b22e99..664b72f 100644
--- a/igc2kmz/coord.py
+++ b/igc2kmz/coord.py
@@ -2,6 +2,14 @@ from math import acos, asin, atan2, cos, pi, sin, sqrt
 
 R = 6371000.0
 
+compass = 'N NNE NE ENE E ESE SE SSE S SSW SW WSW W WNW NW NNW'.split()
+
+def rad_to_compass(rad):
+  while rad < 0.0:
+    rad += 2 * pi
+  return compass[int(8 * rad / pi + 0.5) % 16]
+
+
 class Coord(object):
 
   __slots__ = ('lat', 'lon', 'ele', 'dt')
@@ -16,8 +24,8 @@ class Coord(object):
   def deg(cls, lat, lon, ele, dt=None):
     return cls(pi * lat / 180.0, pi * lon / 180.0, ele, dt)
 
-  def bearing_to(self, other):
-    return atan2(sin(other.lon - self.lon) * cos(other.lat), cos(self.lat) * sin(other.lat) - sin(self.lat) * cos(other.lat) * cos(lon))
+  def initial_bearing_to(self, other):
+    return atan2(sin(other.lon - self.lon) * cos(other.lat), cos(self.lat) * sin(other.lat) - sin(self.lat) * cos(other.lat) * cos(other.lon - self.lon))
 
   def distance_to(self, other):
     """Return the distance from self to other."""