How did selective availability affect civilian GPS accuracy before it ended?

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Cruise ship captain in uniform studies navigational charts with a compass on a table in the ship's bridge. — navigation Officers on a passenger ship using charts for navigation.

Before it was terminated in 2000, selective availability (S/A) was a feature that intentionally degraded the accuracy of the civilian GPS signal. By introducing this artificial error, the system limited the horizontal accuracy available to civilian users to approximately 100 metres (330 feet).1

In contrast, modern unaugmented civilian GPS typically provides horizontal accuracy of about 10 metres (30 feet), a significant improvement over the performance experienced during the period when selective availability was active. The decision to end this practice was driven in part by safety concerns regarding the growing reliance on GPS technology for civilian marine and aviation navigation.1