How this 100-year-old sun compass unlocked polar exploration
It took a National Geographic cartographer to invent a compass that worked where compasses don't.
The magnetized needle of a conventional compass wants to align with Earth’s magnetic field—helpful, unless you’re near the poles, where the field tugs straight downward, rendering magnetic compasses useless. Pilot and National Geographic Explorer Richard E. Byrd, who hoped to fly over the North Pole in the summer of 1925, lamented this during a pre-trip address to the National Geographic Society, and his gripe sent chief cartographer Albert H. Bumstead tinkering. Bumstead developed a novel piece of hardware, a bit like a swiveling watch. Incline it to match one’s latitude and the single, 24-hour hand tracks the sun across the sky. Since the sun at northern latitudes sits due south at noon, an Arctic aviator can align the hand with the sun and set a compass dial by the timepiece. Simple. Elegant. Byrd took one to the Arctic in 1925 and again in ’26. He returned it to the cartographer engraved: “To Albert H. Bumstead. For getting us there.”
A version of this story appears in the January 2026 issue of National Geographic magazine.
