MD80 FO BEGAN TO FOLLOW THE EGPWS TRACK LINE AND CONFUSED IT WITH THE FMC TRACK LINE.

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ACFT HDG DEV. SCHEDULED TO DEPART SLC AT XA01. RECEIVED 45 MIN DELAY DUE TO ARRS AT ORD. PUSHED OFF THE GATE 25 MINS AFTER SCHEDULED TO MAKE AN XC45 WHEELS-UP TIME. SLC WAS DEP/ARR RWY 16L/R. WINDS WERE 350 DEGS AT 5 KTS AND WE WERE AT MAX WT. DUE TO THE TAILWIND WE WEREN'T LEGAL FOR RWY 16 AND REQUESTED A RWY 34 DEP. ON RWY TO RWY 34; CAPT'S TKOF BRIEF INCLUDED (BUT NOT LIMITED TO) TKOF EMERS; TERRAIN AVOIDANCE; AND A L TURN OFF RWY 34 IF WE HAD ANY PROBS TO AVOID THE TERRAIN TO THE E. ONCE READY FOR TKOF AT THE S END; TWR KEPT GIVING US DELAYS. FIRST TO ON THE HR; THEN 5-10 MINS EACH TIME WE ASKED. THEY FINALLY CHANGED RWYS AND WE WERE CLRED FOR TKOF AND TOOK OFF AT XD24 WITH NO ASSIGNED HDG. IT WAS MY LEG (FO). WE HAD RWY HDG IN THE FMA AND PERFORMED A NORMAL MAX PERFORMANCE TKOF. I TOOK OFF IN MAP MODE WITH EGPWS ON AND A 40 MI SCOPE SELECTED. I KNEW OUR FLT PLAN HAD US GOING OVER THE SLC VORTAC AND THEN PROCEEDING ON THE 055 DEG RADIAL TO OCS. ABOUT 1 MI N OF SLC VORTAC; AT ABOUT 6000 FT MSL; I INITIATED A TURN TO 055 DEG HDG WHEN LOOKING AT THE MAP MODE OUR FLT PLAN TOOK US THAT WAY. I MISTOOK THAT AS THE DEP. THE CAPT QUERIED ME ON 'WHAT HDG ARE YOU GOING TO?' AND I TOLD HIM I WAS 'FOLLOWING THE DEP.' THE CAPT LOOKED TO VERIFY WHICH HDG WE WERE TO BE ON AND AT THE SAME TIME I LOOKED AT THE MAP MODE; SAW THE TERRAIN OUT IN FRONT OF US A WAYS AND SOMETHING DIDN'T FEEL RIGHT. I IMMEDIATELY INITIATED A TURN BACK TO RWY HDG WHILE AT THE SAME TIME ATC CALLED AND ASKED OUR HDG. THE CAPT SEEING THE CORRECTION TO THE N ALREADY IN PLACE ASKED ATC 'WHAT HDG DO YOU WANT US ON?' THEY REPLIED WITH A 310 DEG HDG. WE DIDN'T MAKE IT TO THE 055 DEG HDG BEFORE WE TURNED BACK N; BUT WE WERE HDG NE. THE WHOLE INCIDENT FROM THE TIME WE WERE OFF RWY HDG TO THE POINT WE WERE ON A 310 DEG HDG I ESTIMATE AT ABOUT 45 SECONDS. THE CAPT WAS IN THE PROCESS OF VERIFYING WE NEEDED TO BE HDG N THE SAME TIME I WAS CORRECTING TO THE N AND ATC WAS ASKING US WHAT HDG WE WERE ON. IT WAS A BUSY AND CONFUSING COUPLE OF SECONDS. IN HINDSIGHT; I MISTOOK THE FILED CLRNC THAT WAS LOADED IN THE GFMS AS THE DEP ROUTING EVEN THOUGH LOOKING BACK I KNEW IT WASN'T. I TOOK OFF IN THE MAP MODE BECAUSE OF THE TERRAIN AND THAT MADE IT PERFECTLY CLR TO ME THAT THE HDG I WAS TURNING TO WAS INCORRECT. IT HAD BEEN A LITTLE WHILE SINCE I LOOKED AT THE DEP BECAUSE OF THE DELAY SO THAT MAY HAVE CAUSED SOME OF THE CONFUSION ALSO.