How the yaw value is calculated?

[SuhaibMaraqa]

I have a drone 360 images that I display with the pannellum viewer, when the yaw is 0 the image should be looking exactly to the north, but it's not the case as it might be looking the any of the four directions. So how does the yaw value get calculated in the pannellum viewer?

[mpetroff]

A yaw of zero is when the viewer is looking at the center of the equirectangular image (or the front face of a multires image). The northOffset parameter, either set directly or from the image's XMP data, only adjusts the compass display.