Why a better GPS fix made a game possible
A GPS receiver works out its position by timing radio signals from satellites. The signals carry the time they were sent; comparing that with when they arrive lets the receiver estimate its distance from several satellites and calculate a location. Even small timing errors can shift that location noticeably on the ground.
For years, the U.S. government deliberately added error to the civilian GPS signal, a policy known as Selective Availability. When that degradation ended, civilian receivers could pinpoint locations more reliably. That change mattered not just for navigation: it made coordinates useful for directing someone to a particular patch of ground.
From coordinates to a shared treasure hunt
Soon after the change, GPS enthusiast Dave Ulmer hid a container near Beavercreek, Oregon, recorded its coordinates, and invited others to find it. The basic game was simple: hide a container, share its location, and let other people use GPS to search. Visitors could leave an item and sign a logbook, turning a one-person experiment into a repeatable activity.
The crucial shift was that the coordinates could guide people close enough to search on foot, rather than merely toward a broad area. As more people hid containers and shared locations online, each new find gave others a reason to join. A policy change in satellite navigation became the enabling move for a game built around small, physical discoveries.
