SLAC measurements are done in the SLAC SXR coordinate system:
  X is toward north, from the blue undulator frame toward the magnet arrays
  Y is up
  Z is in the beam direction

SLAC analysis is done in the LBNL coordinate system so that the results can be compared:
  X is south, from the magnet arrays toward the blue undulator frame
  Y is up
  Z is opposite the beam direction

The transformation from measurements to analysis coordinate systems is
  Xa = - Xm
  Ya = Ym
  Za = - Zm

ZW
5/31/16