360 degrees heading calculation between two points

Question

I'm using Leaflet + Leaflet's rotate-branch to rotate my map application.

map.setBearing(angle_deg);

is the function to do so. angle_deg has to be between 0 and 359 to simulate any desired angle. I want the map to follow and rotate in relation to the users current position and walking direction.

In order to avoid math, I wanted to use Leaflet.GeometryUtil to do the calculations for me, but only was able to find the functions bearing() and computeAngle(), which yield the same result: horizontal heading between two coordinates (0 up to 180 clockwise and back to 0 again in axial symmetry with a minus sign).

How can I transform this into a full 360 degree value?

To further illustrate:

      0                   360/0
  -90   90       to     270   90 
    +/-180                 180

Could I just add 360 to all negative values and be fine?

Answer 1

In order to get a 360° value, I just had to substract the horizontal angle from 360.

angle_degree = 360-angle

Now the map is rotating in the direction the user is heading to.

Answer 2

The code should look like this:

let heading = (360 + angle) % 360;

resulting in:

(360 + 45)    % 360 // => 405 % 360 = 45
(360 + (-160)) % 360 // => 200 % 360 = 200