PROX OF TCA. PLT DID NOT VIOLATE THE CLASS B AIRSPACE IF HE HAS RPTED HIS LOCATION CORRECTLY.

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I HAD CANCELED AN IFR FLT PLAN IN ORDER TO AVOID VECTORS AROUND CLASS B AIRSPACE ENRTE TO PDK ARPT. MY LORAN WAS SET ON PDK AND INDICATED 29 MI SE OF PDK. AFTER A LONG; HARD IFR TRIP; I WAS TIRED AND SOMEHOW MISTOOK THE INDICATION AS BEING FROM ATL NOT PDK. AT 25 MI I TURNED ON THE GARMIN 95XL I USE AS A BACKUP IN ORDER TO XCHK THE CLASS B AIRSPACE AGAINST MY OTHER REFS. AS IT LOCKED ON AND GAVE 1 PICTORIAL OF MY POS; I WAS IMMEDIATELY AWARE OF BEING CLOSER TO ATL THAN I THOUGHT MY LORAN INDICATED. I HAD STARTED DOWN OUT OF 4500 FT AND I THINK I STILL AVOIDED THE CLASS B AT THE 4000 FT LEVEL; BUT THE INDICATION ON THE GPS LOCKED ON JUST AS I WAS DSNDING SO IT MAY HAVE BEEN CLOSE. I WAS CONCERNED AND IMMEDIATELY DSNDED FURTHER AS WELL AS BEGAN MONITORING THE LCL APCH FREQ FOR POSSIBLE CONFLICTS. THE REST OF THE TRIP WAS UNEVENTFUL AND NO COMMENTS WERE MADE REGARDING A POSSIBLE VIOLATION. MY OWN PHYSICAL AND ATTENTIVE LEVEL CONTRIBUTED TO THIS OVERSIGHT. THE LONG IFR THROUGH BAD WX; THE LONGER TRIP DUE TO THE USUAL VECTORS AROUND ATL; AND THE WELCOME RELIEF OF BEING ABLE TO CONTINUE VFR DIRECT MUST HAVE DULLED MY SENSE OF THE IMPENDING POSSIBLE INCURSION. I FOUND OUT THAT THE TRIP IS NOT OVER UNTIL THE ACFT IS SAFELY TIED DOWN.