Draft: Resolve "Angles calculated using compute_point_angles seem incorect"

Closes #2 (closed)

skais/ais/ais_trajectory.py

@@ -137,17 +137,26 @@ def compute_position_dist_std(dat, radius):
     return dist_means
 
 
+@jit(nopython=True)
+def angle_between_three_points(p1, p2, p3):
+    alpha = bearing(p2, p1)
+    beta = bearing(p2, p3)
+
+    return alpha - beta
+
+
 def compute_point_angles(dat):
     angles = np.zeros(dat.shape[0])
+
+    p1 = (dat[0][0], dat[0][1])
+    p2 = (dat[1][0], dat[1][1])
+    angles[0] = bearing(p2, p1)
     for i in range(1, dat.shape[0] - 1):
         p1 = (dat[i - 1][0], dat[i - 1][1])
         p2 = (dat[i][0], dat[i][1])
         p3 = (dat[i + 1][0], dat[i + 1][1])
 
-        alpha = bearing(p2, p1)
-        beta = bearing(p2, p3)
-
-        angles[i] = 180 - abs(abs(alpha - beta) - 180)
+        angles[i] = angle_between_three_points(p1, p2, p3)
     return angles
 
 
@@ -182,6 +191,7 @@ def angle_dispersion(dat, radius):
 
     return disp
 
+
 class AISTrajectory:
     def __init__(self, df, interpolation_time=None):
         df = df.drop_duplicates(subset=['ts_sec'])