After visiting the old trail more than 20 times, Cheng in 1999 finished mapping its entire route. For this achievement, old trails expert Nelson Yang called him "the most promising young scholar of exploration."
一九九九年，鄭安晞歷經二十次關門古道探險，重現了這條古道，古道專家楊南郡更因此稱許他為台灣「最具有學術探險潛力的年輕人」。