Selective Availability (SA) was an intentional degradation of public GPS signals implemented for national security reasons.
In May 2000, at the direction of President Bill Clinton, the U.S government discontinued its use of Selective Availability in order to make GPS more responsive to civil and commercial users worldwide.
The great “Blue Switch” which controlled selective availability was pressed. Twenty-four satellites around the globe processed their new orders, and instantly the accuracy of GPS technology improved tenfold. Tens of thousands of GPS receivers around the world had an instant upgrade.
Then in September 2007, the U.S. government announced its decision to procure the future generation of GPS satellites, known as GPS III, without the SA feature, no need for a blue switch then.
Doing this made the policy decision of 2000 permanent and eliminated any source of uncertainty in GPS performance that had been of concern to civil GPS users worldwide.
We will be holding an event to celebrate this Blue Switch Day on Saturday the 8th May 2021, the 21st anniversary, in Castletown Square at 12.00 Noon. As well as attending the event Geocaching has a special Souvenir which you can also earn.
If any Covid19 restrictions are put back into place then this event will sadly have to be cancelled.
(Just for the record there was not an actual Blue Switch.)