Timeline milestone
A 24-satellite constellation reaches initial operational capability
From How GPS Became Invisible Infrastructure: Satellites, Smartphones and Precise Time
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Milestone
A 24-satellite constellation reaches initial operational capability
With enough satellites available, GPS could provide three-dimensional position and timing worldwide. Full operational capability followed in 1995, turning decades of tests into a dependable service.
With 24 satellites finally in orbit, enough were visible from any point on Earth at any time to calculate a position in three dimensions, latitude, longitude, and altitude, rather than the intermittent two-dimensional fixes earlier systems like Transit provided. This was declared initial operational capability, meaning the system was reliable enough for the military to depend on, though engineers were still fine-tuning it. Full operational capability, the point where every promised feature worked to specification, followed in 1995. Two decades after the Pentagon merged competing programs, GPS had become the continuous, dependable utility it was originally designed to be, rather than an intermittent research tool.
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