PLT OF M20-C USES WRONG GPS COORDINATES AND LANDS AT WRONG ARPT. DISCOVERED AFTER THE FACT.

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VFR PRACTICE/PLEASURE FLT -- MISIDENTED AN ARPT FOR LNDG IN CLASS E/G AIRSPACE AS ANOTHER INTENDED ARPT. BOTH HAVE SIMILAR RWY CONFIGNS AND ARE LOCATED ON N SIDE OF TOWN. FIRST TIME FLT TO EITHER ARPT. OVERFLEW ARPT WHEN NO RESPONSE TO 'TFC' CALLS WAS RECEIVED TO CHK FOR TFC AND WIND DIRECTION. MADE ALL 'TFC' RADIO XMISSIONS INDICATING APCH AND INTENT TO ENTER THE LNDG PATTERN MIS-IDENTING ARPT. EXECUTED 1 TOUCH AND GO AND DEPARTED AREA. CORRECT AND 'INCORRECT' AIRFIELDS WERE 18 NM APART. ERROR DUE TO: INCORRECT COORDINATES ENTERED IN VFR GPS. RELIANCE ON ONE FORM OF NAV RATHER THAN XCHK WITH PILOTAGE AND VORS; ETC. PLT NOT LOOKING OUTSIDE TO VISUALLY CONFIRM LOCATION. DISCOVERED WHEN RECHKING SECTIONAL VERSUS OUTSIDE LANDMARKS. FACTORS AFFECTING SIT: PLT WAS FOCUSED ON FLYING A COMPLEX ACFT AND SETTING UP FOR PRACTICE LNDG (ONLY 12 HRS TIME IN TYPE). LESSONS LEARNED: PLT CAN'T RELY ON ONE MEANS OF NAV AND MUST GET POSITIVE IDENT ON ARPTS. FURTHER; PLT SHOULD HAVE QUESTIONED EARLY TIME OF ARR. VERY DANGEROUS SIT BECAUSE ACFT IN VICINITY OF ARPT WOULD NOT HAVE HEARD MY XMISSIONS BECAUSE OF DIFFERENT CTAF'S FOR THE 2 ARPTS.