Gladys West and the GPS revolution: Blue Switch Day 2026
When geocachers step outside with a GPS-enabled device, they’re tapping into decades of brilliant science and mathematics that make those coordinates possible. Behind every successful find stands a brilliant mathematician whose work helped make modern GPS possible: Dr. Gladys West.
Image from the New York Times.
Gladys West’s groundbreaking work focused on solving a deceptively complex problem: determining the Earth’s precise shape.
In the 1960s and 1970s, West helped process vast amounts of satellite data to model Earth’s geoid. Because satellites orbit based on Earth’s gravitational field, understanding this shape was essential for calculating accurate positions on the planet’s surface. West programmed early supercomputers to analyze oceanographic and satellite measurements, producing increasingly precise models that became foundational to the development of the Global Positioning System (GPS). When GPS satellites were later deployed, they relied on these accurate Earth models to translate satellite signals into the exact coordinates we use today for navigation, mapping, and location-based technologies.
Geocaching is built on a beautifully simple idea: use GPS coordinates to find hidden treasures around the world, but the magic behind those coordinates depends on an incredibly sophisticated system of satellites, timing signals, and Earth models.
Thank you, Gladys West, for advancing geodesy and satellite modeling, making the precision of geocaching possible!
Celebrate Blue Switch Day 2026 by hiding a geocache, and earn your Blue Switch Day 2026 hider souvenir.
Blue Switch Day 2026 hider:
- To earn this souvenir, geocachers must have a non-Event geocache published between May 1 and 31, 2026.
- Any non-Event geocache type (excluding Adventure Lab®) counts, as long as it is published between May 1 and May 31.
- Remember that review times may vary! A geocaching community volunteer will typically begin reviewing your geocache within 7 days. We recommend submitting your cache for publication at least a week before the deadline. Learn more about the cache review process in our Help Center.
How will you celebrate Blue Switch Day this year?
