A NON NEAR EVENT BTWN TAXIING TFC DURING RAMP OP RAMP DEP PROC.

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RAMP CTL CLRED US TO 'TAXI TO SPOT 3F VIA F; GIVE WAY TO OTHER ACR HVY ON TXWY A. OUR ACFT WAS ON GATE; POINTING N WITH NO VISIBILITY TO S OR W; LIMITED TO E; ACFT HAD TO BE TURNED 180 DEGS TO R FOR PROPER TAXI DIRECTION AND TO SEE ANY TFC. WHILE PIC MADE TURN; I LOOKED AT ARPT DIAGRAM TO LOCATE TXWY A WHICH WE WERE NOT FAMILIAR WITH; WHICH THERE WERE NO NEAR MARKINGS FOR; AND WHICH WAS NOT ANNOTATED ON THE ARPT DIAGRAM AT OR NEAR OUR LOCATION. AS THE ACFT COMPLETED THIS TURN; IT WAS CLOSE TO THE XING TXWY WHICH TURNED OUT TO BE TXWY A AND ALIGNED DOWN TXWY G VICE TXWY F. IT WAS AT THAT TIME THAT WE FIRST SAW THE HVY WHICH WAS STILL 100 YDS AWAY AND MOVING SLOWLY IF AT ALL. PIC APPLIED BRAKES. WE ADVISED RAMP WE NOW SAW THE HVY AND MAY BE IN ITS WAY BEING SO CLOSE TO THE TXWY AND THAT WE WERE ALIGNED WITH TXWY G. RAMP DIRECTED US TO MOVE AHEAD OF THIS HVY AND USE TXWY G. RAMP SHOULD HAVE BEEN MORE VIGILANT GIVEN OUR 'BLINDNESS' AT THE GATE TO TFC AND TAXI DIRECTION. ARPT DIAGRAM COULD BE MORE CLR AS TO LOCATE OF TXWY A. DON'T MOVE ACFT IF NOT SURE OF CONFLICTING TFC AND DIRECTION.