Retired surveying engineer Gu Xiuyuan rushed to the Qingxia Dam area with his la…

Retired surveying engineer Gu Xiuyuan rushed to the Qingxia Dam area with his last remaining hand-drawn blueprints and a planimeter to handle a water inrush emergency. A typhoon caused widespread flight cancellations, and only one emergency flight was permitted to take off. Passenger Lin Xiao had no…