kijangnim:
Yes that's what I was going to say
The IRS/INS/ADIRU whatever you use does not update after alignment.(on the ground you can get a fast align ( manual or automatically on the 777 )to remove the GS errors ) It's the NAV SYSTEM that updates. In my case the on the 777 the ADIRU drifts and the FMC uses the best info to update itself and that is always the GPS. Unless on App then it's LOC-GPS or LOC-DME