FLC OF ACR MLG ACFT TAXIED BEYOND CLRNC LIMIT AFTER GATE PUSH-BACK.

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AT THE NEW ACR TERMINAL IN LGA WE CALLED FOR PUSHBACK CLRNC AND WERE TOLD TO PUSH FOR SPOT 24. WHEN WE WERE RELEASED FROM THE TUG I BEGAN TO TAXI TO WHAT THE FO AND I BELIEVED TO BE SPOT 24; AFTER CHKING OUR COMMERCIAL PUBLICATION PAGES FOR THIS AREA. WE WERE THEN INFORMED BY GND CTL THAT WE HAD PASSED SPOT 24 AND WERE IN HIS CTL AREA (WITHOUT A CLRNC). THE FO AND I WERE UNFAMILIAR WITH THIS NEW AREA SO WE BOTH HAD THE APPLICABLE CHART OUT. THE CHART DEPICTS WHITE AREAS; THAT WE TOOK TO MEAN GRASS OR DIRT SURFACED AREAS; AND USED AS A REF FOR SPOT 24. WE DISCOVERED THAT THIS WHITE AREA ON THE CHART MAY MEAN DIRT OR A HARD RAMP AREA IN ACTUALITY. THIS PRESENTATION IS NOT DEFINED IN THE COMMERCIAL PUBLICATION'S INTRODUCTION. THIS WAS COMPOUNDED BY A WET SURFACE; RAIN AND OVCST THAT MADE PAINTED LINES AND NUMBERS VERY DIFFICULT TO SEE. I WOULD LIKE TO SEE BETTER RAMP AND TAXIWAY MARKINGS AND A BETTER CHART DEPICTION OF AREAS THAT ARE DIRT; GRASS; OR HARD SURFACED RAMP 'ISLANDS' THAT SHOULD BE AVOIDED.