GA CHARTER SMT MADE A TKOF ON THE WRONG RWY AT OMA.

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MIDDLE OF NIGHT; UNFAMILIAR ARPT. I WAS CALLED OUT ON AN AIR AMBULANCE FLT FROM LIT TO OMA AND BACK. TAXIING FOR DEP FROM E GA RAMP; GND CTL AND TWR WAS THE SAME PERSON. I WAS UNFAMILIAR WITH THE ARPT AND WAS RECEIVING PROGRESSIVE TAXI INSTRUCTIONS TO RWY 14L. AS I HAD COMPLETED THE BEFORE TKOF CHKS ON THE RAMP I WAS READY FOR DEP AT THE END OF 14L. AS I ROUNDED THE CORNER I SWITCHED TO THE TWR FREQ. BEFORE I COULD CALL HIM THE TWR ASKED ME IF I WAS READY AND SAID YES AND WAS CLRED FOR TKOF. THE APCH END OF 14L CONNECTS TO RWY 17 WHICH IS MUCH WIDER AND MORE VISIBLE. CONSIDERING THE ABOVE FACTORS IT IS VERY EASY TO INADVERTENTLY LINE UP ON EITHER RWY AT THAT POINT. AGAIN BEING UNFAMILIAR AND MAKING A ROLLING TKOF WITHOUT STOPPING AT THE APCH END I BEGAN THE TKOF ON 17. AFTER GETTING TKOF PWR SET AND CHKING THE ENG INSTS FOR ANY ABNORMALITY I NOTICED MY HDG INDICATOR WAS ABOUT HALFWAY BTWN 140 AND 170 AT WHICH POINT THE THOUGHT FLASHED THROUGH MY MIND THAT I COULD BE ON THE WRONG RWY. THIS WAS AT THE POINT OF ROTATION SO I CONTINUED THE TKOF IN THE INTEREST OF SAFETY. AFTER TKOF THE TWR HANDED ME OFF TO DEP AND INFORMED ME THAT I TOOK OFF ON 17. I THINK THAT THERE SHOULD BE BETTER MARKINGS DISTINGUISHING THE 2 RWYS.