ACR Y HAD LTSS FROM ACR X DURING TKOF ROLL. SYS ERROR.

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AT SFO EARLY MORNING BEFORE DAYLIGHT. WX WAS LOW CEILING AND VISIBILITY. ACR X SFO-LAX WE ENCOUNTERED THE FOLLOWING CHAIN OF EVENTS: TAXIING ON OUTER TO RWY 01L WE TURNED ONTO TAXIWAY 'HOTEL' HOLDING SHORT OF RWY. WE WERE CLRED INTO POS TO HOLD. AS WE STARTED TO TAXI INTO POS ON RWY 01L WE NOTICED THE LIGHTS OF AN ACFT APCHING FROM THE R. THIS ACFT WAS TAKING OFF. WE STOPPED OUR TAXI AND PREVENTED A COLLISION OF OUR ACFT AND THE APCHING ACFT. WE WERE SUBSEQUENTLY CLRED INTO POS AGAIN; AND THEN CLRED FOR TKOF. AFTER ARRIVING AT LAX WE TALKED BY TELEPHONE TO SFO TWR SUPVR. WE ALSO TALKED TO OUR FLT MGRS AT SFO AND LAX. WE LEARNED THAT SFO LCL PROC IS TO USE TAXIWAY 'MIKE' TO ENTER RWY 01L FOR TKOF. THERE IS NO PUBLISHED PROC FOR USING TAXIWAY 'MIKE' INSTEAD OF 'HOTEL' TO ENTER THE RWY. ALSO THE TWR SUPVR SAID THE TWR CANNOT SEE THE DEP END OF RWY 01L IN LOW VISIBILITY CONDITIONS. WE ALSO DISCUSSED THE TWR; GND SURVEILLANCE RADAR AND WHY THE CTLR DID NOT KNOW THAT WE WERE ENTERING THE RWY AT TAXIWAY 'HOTEL'. THE SUPVR EXPLAINED THAT THEIR GND RADAR GIVES AMBIGUOUS RETURNS AND CANNOT BE RELIED UPON 100 PERCENT. IN CONCLUSION THE SFO TWR SHOULD ADVISE ACFT DEPARTING RWY 01L THAT THE RWY ENTRY POINT FOR TKOF IS TAXIWAY 'MIKE' NOT TAXIWAY 'HOTEL' WHICH IS AT THE END OF THE RWY. IN LOW VISIBILITY OPS THE SAME INCIDENT COULD BE REPEATED TO END IN AN ACCIDENT.