Calculating line direction

In addition to distance, you will often want to know the bearing of a line between its endpoints. We can calculate this line direction from one of the points using only the Python math module:

1. First, we import the math functions we'll need:

from math import atan2, cos, sin, degrees

2. Next, we set up some variables for our two points:

lon1 = -90.21
lat1 = 32.31
lon2 = -88.95
lat2 = 30.43

3. Next, we'll calculate the angle between the two points:

angle = atan2(cos(lat1)*sin(lat2)-sin(lat1) * \
  cos(lat2)*cos(lon2-lon1), sin(lon2-lon1)*cos(lat2))

4. Finally, we'll calculate the bearing of the line in degrees:

bearing = (degrees(angle) + 360) % 360
print(bearing)
309.3672990606595

Sometimes, you end up with a negative bearing value. To avoid this issue, we add 360 to the result to avoid a negative number and use the Python modulo operator to keep...