Narrative:

During taxi and on the runway at pvg all system and indications were normal. Specifically; the map display showed the runway in proper alignment with the aircraft as we taxied out and lined up for takeoff. In addition; the magenta route line was positioned correctly. At liftoff we received a GPWS warnings: 'too low; terrain.' at 400 ft and 1000 ft respectively we engaged LNAV and VNAV; and appeared to track our course normally. After an approximately 90 degree left turn from runway heading; we were expecting another left turn on course to tao and were cleared to proceed direct to pinot intersection. According to the FMC; this would be a right turn away from tao. We queried departure control; asking 'cleared for a right turn direct pernot?' ATC did not change the clearance. We began the turn and asked for our routing after pernot because FMC was showing a 180 degree course reversal at pinot to proceed to the next fix; odulo. This did not make sense. We were told that odulo was in fact the next fix; so we asked ATC to spell pinot. They did; confirming we had the correct intersection entered in the FMC. At that time ATC saw we were turning right and called and told us to turn left for direct to pinot. We told pvg control we were unable direct pinot; and that we were no longer RNAV equipped; and were given vectors on course. We then discovered that we had a 30+ NM disparity between the FMC position and the GPS position which was displayed on the adsb menu page. It appeared that the GPS position was the more correct position. The 30+ NM disparity continued for the remainder of the flight which we conducted using radar vectors and raw data.

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Original NASA ASRS Text

Title: B757 FLT CREW HAS A TRACK HDG DEV DURING DEP FROM ZSPD.

Narrative: DURING TAXI AND ON THE RWY AT PVG ALL SYS AND INDICATIONS WERE NORMAL. SPECIFICALLY; THE MAP DISPLAY SHOWED THE RWY IN PROPER ALIGNMENT WITH THE ACFT AS WE TAXIED OUT AND LINED UP FOR TKOF. IN ADDITION; THE MAGENTA RTE LINE WAS POSITIONED CORRECTLY. AT LIFTOFF WE RECEIVED A GPWS WARNINGS: 'TOO LOW; TERRAIN.' AT 400 FT AND 1000 FT RESPECTIVELY WE ENGAGED LNAV AND VNAV; AND APPEARED TO TRACK OUR COURSE NORMALLY. AFTER AN APPROX 90 DEG L TURN FROM RWY HDG; WE WERE EXPECTING ANOTHER L TURN ON COURSE TO TAO AND WERE CLRED TO PROCEED DIRECT TO PINOT INTXN. ACCORDING TO THE FMC; THIS WOULD BE A R TURN AWAY FROM TAO. WE QUERIED DEP CTL; ASKING 'CLRED FOR A R TURN DIRECT PERNOT?' ATC DID NOT CHANGE THE CLRNC. WE BEGAN THE TURN AND ASKED FOR OUR ROUTING AFTER PERNOT BECAUSE FMC WAS SHOWING A 180 DEG COURSE REVERSAL AT PINOT TO PROCEED TO THE NEXT FIX; ODULO. THIS DID NOT MAKE SENSE. WE WERE TOLD THAT ODULO WAS IN FACT THE NEXT FIX; SO WE ASKED ATC TO SPELL PINOT. THEY DID; CONFIRMING WE HAD THE CORRECT INTXN ENTERED IN THE FMC. AT THAT TIME ATC SAW WE WERE TURNING R AND CALLED AND TOLD US TO TURN L FOR DIRECT TO PINOT. WE TOLD PVG CTL WE WERE UNABLE DIRECT PINOT; AND THAT WE WERE NO LONGER RNAV EQUIPPED; AND WERE GIVEN VECTORS ON COURSE. WE THEN DISCOVERED THAT WE HAD A 30+ NM DISPARITY BTWN THE FMC POS AND THE GPS POS WHICH WAS DISPLAYED ON THE ADSB MENU PAGE. IT APPEARED THAT THE GPS POS WAS THE MORE CORRECT POS. THE 30+ NM DISPARITY CONTINUED FOR THE REMAINDER OF THE FLT WHICH WE CONDUCTED USING RADAR VECTORS AND RAW DATA.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.