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. Then, 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)

   The output is 309.3672990606595 degrees.

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...