Selective Availability
The United States switches off GPS Selective Availability worldwide
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Original prompt & settings (JSON) ↗More than four million existing receivers got a free accuracy upgrade in the same minute. At one Kentucky station the 95% error radius fell from 45.0 metres to 6.3.
04:05 UTC, 2 May 2000
A few minutes after midnight EDT on 2 May 2000, commands took effect across the GPS constellation setting Selective Availability — the intentional degradation of the public signal — to zero worldwide. Monitoring stations recorded the intentional error disappearing at approximately 04:05 UTC, over an interval of one or two minutes.
Existing civilian receivers picked up the more accurate signal without replacement, user fees or additional government expenditure. More than four million users worldwide had receivers when the change was announced.
How much better
The White House estimated the result would be up to ten times more accurate, with basic civilian accuracy of approximately 20 metres or better. At one Kentucky reference station, the 95% radius went from 45.0 metres with SA to 6.3 metres without it.
The change removed intentional degradation but left the ordinary error sources: atmospheric delay, satellite geometry, orbit error and multipath. Post-change accuracy is therefore not one universal number.
Set to zero, not removed
A coordinated security review had concluded that the military could deny GPS regionally in threat areas, making continuous worldwide degradation unnecessary and of minimal security benefit. Bill Clinton approved the recommendation and announced on 1 May that degradation would end at midnight.
Selective Availability was set to zero rather than physically removed from the satellites; a 2007 procurement decision later excluded the feature from GPS III. Civilians gained nothing from the encrypted military service — what stopped was the deliberate degradation of the open civilian signal.
Sources
Researched 23 Aug 2026 5 sources 2 audit passes
How this was checked
Researched from the web into a fact sheet, rewritten from that sheet, then audited against it by a different model. How the pipeline works →
What the sources leave uncertain
- The White House announced the decision on 1 May, but GPS.gov records that the operational change occurred a few minutes after midnight EDT on 2 May. Thus 2 May is the best event date.
- “Blue Switch Day” is an informal term popularized by geocachers. There was no documented literal blue master switch.