PS-Insar analyze for vertical displacement

Hello everyone,
Let assume, that after a PSInSAR analyze we have a vertical displacement solution for both ascending and both descending cases. I know, that combining of the asc and desc solutions makes possible to solve 3D displacements, but there are some points that I don’t understand?

  1. If I want to get only the vertical displacements by combining them, I just have to calculate a simple average from the solution of the asc and desc?
  2. How can I put it in practice, if with PS-InSAR analyze I cannot guarantee that the same points are found on asc and decs pictures? (I can unserstand that it’s working if you’re doing simple DInSAR, but a stack of images I cannot see through the process)

Thanks, for any help,

a simple average of both is not the correct solution. A similar question was asked here: Phase to Displacement Units?
Please have a look at the post of mengdahl with the PDF, the document quite nicely explains why it is a complex task to combine ascending and descending displacements. There is also a discussion ongoing below that.