On the peak’s highest crest of snow, Gautam, aided by another Nepali surveyor and three Sherpa guides, set up a GPS antenna, which began recording its precise position from a network of satellites. Next, the men deployed ground-penetrating radar to measure the depth of the snow beneath their crampons. The two dark, frigid hours they worked on the world’s highest mountain were not without personal sacrifice: Gautam would later lose a toe to frostbite.

Now more than 15 months later, the results of their efforts—a new official height for Mount Everest—are eagerly anticipated. The project, spearheaded by Nepal’s Survey Department, was intended to pinpoint the summit elevation as accurately as possible with state-of-the-art instruments and techniques but also to make a