# Bearing of Two close lines in python

In the picture below I am finding the bearing of two close lines. This is the picture of two complete lines. The brown line might be a bit large from the blue line.

Should not be the bearing of these two lines should be close to each other with a difference of may be few degrees?

I am checking whether they are equal or not by getting the difference of both lines bearing. I am using python to calculate the bearing and get the difference between there bearing. The code I am using to get out the bearing is:

``````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))
:Parameters:
- `pointA: The tuple representing the latitude/longitude for the
first point. Latitude and longitude must be in decimal degrees
- `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 (type(pointA) != tuple) or (type(pointB) != tuple):
raise TypeError("Only tuples are supported as arguments")

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 normalize the initial bearing as shown below
initial_bearing = math.degrees(initial_bearing)
compass_bearing = (initial_bearing + 360) % 360

return compass_bearing
``````

In the end what I am doing is calculate there difference like that:

``````DifferenceInBearing = abs(BlueLineBearing - BrownLineBearing)
``````

My problem is that the difference between them is huge just around 179.71922333147256 degrees.

The WKT values of blue line is:

``````LINESTRING (327854.7919419953 6809188.658530097, 327854.2288694207 6809187.856443238)
``````

The Wkt value for brown line:

``````LINESTRING (327854.139971 6809187.723519, 327854.714599625 6809188.541579125)
``````

Shouldn't the bearing be close enough? • @BERA that is what the problem the difference between there bearing is huge approximately 179. Do you have some idea why is it? Sep 27, 2017 at 8:58

One line starts at bottom left and one starts at top right so a diffence of about 180 should be correct.

I use this calculation, taken from Find the bearing angle between two points in a 2D space:

``````import math

def calculate_initial_compass_bearing(pointA, pointB):
startx,starty,endx,endy=pointA,pointA,pointB,pointB
angle=math.atan2(endy-starty, endx-startx)
if angle>=0:
return math.degrees(angle)
else:
return math.degrees((angle+2*math.pi))
``````

Which for the first line gives:

``````calculate_initial_compass_bearing((327854.139971,6809187.723519), (327854.714599625,6809188.541579125))
54.91470758400356
``````

And second line:

``````calculate_initial_compass_bearing((327854.7919419953, 6809188.658530097), (327854.2288694207, 6809187.856443238))
234.93078130214872
``````
• why you changed your code? Sep 28, 2017 at 10:12