how to keep two headsets's coordinate systems are consistent to ensure actual scene and virtual scene correspondence.

Hello
I have two computers and two HP Windows Mixed Reality headsets. I’m going to develop a VR application that cantains virtual scene corresponding to the real scene.Two pepole can walk in real scene with headset, and can see each other.
I have collected environmental data on the two computers. But I have a problem : how to keep two headsets’s coordinate systems are consistent to ensure actual scene and virtual scene correspondence.