# LICENSE: public domain
# https://gist.github.com/jeromer/2005586
__all__ = ["calculate_initial_compass_bearing"]
import math
[docs]
def calculate_initial_compass_bearing(pointA, pointB):
"""Calculates the bearing between two points.
The formulae used is the following:
θ = atan2(sin(Δlong).cos(lat2),
cos(lat1).sin(lat2) − sin(lat1).cos(lat2).cos(Δlong))
:param pointA: The tuple representing the latitude/longitude for the
first point. Latitude and longitude must be in decimal degrees
:param pointB: The tuple representing the latitude/longitude for the
second point. Latitude and longitude must be in decimal degrees
:Returns:
The bearing in degrees
:Returns Type:
float
"""
if not isinstance(pointA, tuple) or not isinstance(pointB, tuple):
raise TypeError("Only tuples are supported as arguments")
lat1 = math.radians(pointA[0])
lat2 = math.radians(pointB[0])
diffLong = math.radians(pointB[1] - pointA[1])
x = math.sin(diffLong) * math.cos(lat2)
y = math.cos(lat1) * math.sin(lat2) - (
math.sin(lat1) * math.cos(lat2) * math.cos(diffLong)
)
initial_bearing = math.atan2(x, y)
# Now we have the initial bearing but math.atan2 return values
# from -180° to + 180° which is not what we want for a compass bearing
# The solution is to normalise the initial bearing as shown below
initial_bearing = math.degrees(initial_bearing)
compass_bearing = (initial_bearing + 360) % 360
return compass_bearing