Two Rate Gyro Assemblies (RGAs) are used by the International Space Station (ISS) onboard Navigation function as a source of vehicle attitude rates. Prior to flight, it was necessary to make physical measurements of the actual achieved mounting orientation of these RGAs, relative to a fiducial reference frame embedded in the ISS truss structure. The resulting measurements were used to calculate initialization data for the flight software, and also provided a basis for a statistical statement relative to correct installation of the RGAs. The measurement process was accomplished using LASER ranging and angles data to establish inertial positions of several locations on the RGA optical cubes. A Least Squares Differential Correction (LSDC) process was used to yield an optimal estimate of the orientation of each RGA. Since the measurements set was not large, confidence intervals were used for statistical interpretation of the results.