hiking notification form; climbing plan
A document submitted to the police or mountain authorities before a hike or climb, detailing the planned route, party members, and schedule. Required in many Japanese mountain areas for safety.
I submitted a hiking notification form to the police before entering the mountain.
In case of an accident, I also give a copy of the climbing plan to my family.
登山届 is a more general term for a climbing notification, while 登山計画書 specifically refers to the detailed plan document.
Compound of 登山 (mountain climbing) + 計画 (plan) + 書 (document).