A DEPARTING B757 RECEIVES A FALSE GPWS WARNING WHICH THE CREW DETERMINED TO BE LINKED TO THEIR VERY LARGE MAP SHIFT THAT OCCURRED ON DEP FROM SEQU; FO.

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I EXPERIENCED A MAP SHIFT -- THE LIKES I'VE NEVER SEEN. MOST OF US HAVE SEEN SUBTLE SHIFTS -- MAYBE 1/4 MI OR SO; BUT JUST AFTER LIFTOFF FROM RWY IN UIO; I GOT THE 'TERRAIN; PULL UP; TERRAIN PULL UP.' I WAS IN TERRAIN MODE WITH THE 10 MI RANGE SELECTED. WE WERE; FORTUNATELY; IN VMC ON A CAVU DAY. I KNEW WE WERE SAFE FROM ANY TERRAIN; BUT THE INDICATION WAS SOLID RED. WE CONTINUED TO CLB IN NORMAL FASHION BUT THE WARNING PERSISTED. I FINALLY DISABLED THE WARNING BY PRESSING THE OVERRIDE SWITCH ON THE FORWARD PANEL. (AGAIN WE WERE IN VFR CONDITIONS; THE WX WAS AS CLR AS COULD BE.) I THEN SELECTED THE RANGE SELECTOR TO 20 AND SAW THAT UIO ARPT; WHICH WAS RIGHT BEHIND US LESS THAN 3 MI; WAS DEPICTED OVER 10 MI TO OUR L (E). WE FLEW THE DEP ON NOTHING BUT RAW DATA AND; USING EVERY MEANS POSSIBLE; DETERMINED THAT A MAP SHIFT OCCURRED JUST AFTER LIFTOFF TO THE TUNE OF 11 MI. WE MONITORED CAREFULLY THE SIT; FLYING ONLY RAW DATA. AT TCO; SEVERAL MINS INTO THE FLT; WE DETERMINED THAT ABOUT 10.2 MI OF MAP SHIFT WAS STILL THERE. STILL FLYING RAW DATA OR '727 MODE' BY THE TIME WE GOT TO PANAMA -- USING 3 VORS; DME DATA; AND FMC DATA -- WE BOTH DETERMINED THAT THE MAP SHIFT HAD CORRECTED ITSELF AND THE FMC WAS NOW INDICATING CORRECTLY. JUST WANTED TO RPT THIS; REMINDING CREWS THAT MAP SHIFTS STILL OCCUR AND THIS IS A STRONG INDICATION THAT THEY CAN BE VERY SEVERE.