measure_bearing.py

from qgis.core import *
from qgis.gui import *
import math

@qgsfunction(args='auto', group='Custom', referenced_columns=[])
def bearing(point1, point2, feature, parent):
    """
    Returns the bearing, on the EPSG:7030 (WGS 84) ellipsoid, in degrees,
    clock-wise from North, between two points with coordinates
    expressed in the EPSG:4326 (WGS 84) CRS.
    <br>
    <h2>Syntax</h2>
    <p>bearing( point_a, point_b )</p>
    <h2>Arguments</h2>
    <p>point_a    point geometry</p>
    <p>point_b    point geometry</p>
    <h2>Examples</h2>
    <ul>
      <li>bearing( make_point( 16.123, 42.123 ), make_point( 16.345, 42.345 ) ) -> 36,543008086155425</li>
    </ul>
    """
    d = QgsDistanceArea()
    d.setEllipsoid('WGS84')
    return math.degrees(d.bearing(point1.asPoint(), point2.asPoint())) % 360