Mapping

The Survey of India trained Indian surveyors to cross the plateau on foot and measure it while they walked, because they were forbidden to be there.

He walked measured paces counted on a rosary shortened to a hundred beads, and hid his notes inside a prayer wheel.

A sextant, a boiling-point thermometer and a compass are enough to fix a position and an altitude if you are patient.

Water boils lower as you climb, so a thermometer becomes an altimeter and a route becomes a profile.