FLC OF GOV NAV FACILITY CHK ACFT ALLEGEDLY PENETRATED ATL TCA.

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FAA ACFT; FLT INSPECTION; VFR 9500 FT ENRTE TO FTY ARPT. RPTED TO ATL APCH ON THE ATC 222 DEG RADIAL 39.8 DME. UTILIZING THE SECTIONAL CHARTS DEPICTION OF THE ATLANTA TCA BEGAN A RAPID DSCNT TO 2500 FT. ATC ADVISED US THAT WE WERE IN TCA AT 30 NM. MY RESPONSE WAS 'CHKING THE CHART I THOUGHT WE WERE BELOW IT'. I THEN GAVE HIM MY ATL DME AS 30.1 DME. ALSO OBSERVED ALT DSNDING THROUGH 6400 FT. AFTER LEVELING OFF AT 2500 FT. I OBSERVED OUR DISTANCE FROM FULTON COUNTY ARPT ON THE RNAV AS 23.8 NM. IF THIS IS INDEED A 'TCA' PENETRATION; THEN A CONTRIBUTING FACTOR IS THE SECTIONAL CHARTS DEPICTION OF THE TCA AND THE BLUE MODE C ARC IMPOSING AS AN AREA OF 10000 FT FLOOR VICE 8000 FT FLOOR. THIS PARTICULAR SW CORRIDOR LEADS ONE TO BELIEVE THE FLOOR OF THE TCA IN THAT AREA IS 10000 FT AND NOT 8000 FT. ATC (OF COURSE) DISCOVERED THE ALLEGED PENETRATION. A WARNING BY ATC WAS ISSUED AT THE SAME TIME A TRANSPONDER CODE WAS ISSUED; HOWEVER; I FEEL THAT IF THE CTLR WAS ABOUT TO OBSERVE AN ACFT COMMIT AN ATC VIOLATION OF AIRSPACE; THEN THE PLT SHOULD HAVE BEEN ADVISED PRIOR TO THIS INSTANCE. CORRECTIVE ACTION SHOULD BE TO CLEAN UP THE SECTIONAL CHART AS AFOREMENTIONED.