Align co-ordinates for spherical harmonics coefficients and depth estimation in ARKit, iOS

In the ARKit face tracking configuration

ARFaceTrackingConfiguration

, we can get both depth and environment-lighting information (as coefficients of spherical-harmonics basis functions). My initial experiments indicate that "depth" and "environment-lighting" computation is not happening in the same co-ordinate space. How are these two co-ordinate systems differ? And, how we can transform either depth or environment-lighting in a common co-ordinate system so as to use them together?