AN ACR WDB MISREAD ITS PRE-DEP CLRNC AND FLEW THE WRONG SID.

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FLT HVY DEPARTED LAX ON THE LAXX 1 DEP (WHICH WAS THE FILED DEP). THE 2 ACFT IN FRONT OF US WERE INSTRUCTED TO FLY A HDG OF 250 DEGS. WE WERE NOT GIVEN A HDG TO FLY. SHORTLY AFTER CONTACTING DEP CTL; HE ASKED US IF WE WERE GIVEN A HDG. WE SAID NO; THAT OUR PRE-DEP CLRNC SAID LAXX 1. THE CTLR INFORMED US THAT; AT THAT TIME OF DAY; WE SHOULD BE ON THE LOOP DEP; WHICH IS A HDG OF 235 DEGS AFTER XING THE 160 DEG RADIAL OF SMO AND CLB TO 2000 FT. LATER; WHEN WE HAD TIME; WE RECHKED THE PRE-DEP CLRNC AND FOUND THAT FURTHER DOWN INTO THE TEXT; OUR DEP HAD BEEN CHANGED TO THE LOOP DEP. SUPPLEMENTAL INFO FROM ACN 222419: BEFORE TAXI I READ OUR PRE-DEP CLRNC. IT STATED LAXX 1; DAGGETT; ETC...DEN. AFTER TKOF; WE TURNED AS PER LAXX 1 SID. DEP CTL ASKED WHAT DEP WE WERE FLYING. DEP STATED WE SHOULD BE FLYING LOOP. WE PROCEEDED TO FLY LOOP WITH NO CONFLICTS AND MADE ALL RESTRICTIONS HANDILY. AFTER 10000 FT; WE REVIEWED SID. IT INCLUDED LOOP DEP AND LAXX 1 DEP. PRE-DEP CLRNC NOT CLR. WE SHOULD HAVE QUESTIONED DEP.