This is great news. In short, the "Selective Availability" error
applied to the GPS signal restricted GPS units without the secret
keys to an accuracy of only 100m 2DRMS (+/- 50 metres.)
With SA lifted, the accuracy is limited by the unit - a frequently
quoted figure is 15m RMS (+/- 7.5 metres.) Differential GPS
(using a fixed beacon transmitting correction values to suitably
equipment GPS units) is still better than this (1-5 metres), but
not by as great a margin as it used to be.
I have yet to confirm that SA has been turned off yet, but the
improvement should be quite noticable.
> May 1, 2000
>
> STATEMENT BY THE PRESIDENT REGARDING THE UNITED STATES' DECISION
> TO STOP DEGRADING GLOBAL POSITIONING SYSTEM ACCURACY
>
> THE WHITE HOUSE
>
> Office of the Press Secretary
>
> _______________________________________________________
> For Immediate Release May 1, 2000
>
>
> STATEMENT BY THE PRESIDENT REGARDING
> THE UNITED STATES' DECISION TO STOP DEGRADING
> GLOBAL POSITIONING SYSTEM ACCURACY
>
>
> Today, I am pleased to announce that the United States will stop the
> intentional degradation of the Global Positioning System (GPS) signals
> available to the public beginning at midnight tonight. We call this
> degradation feature Selective Availability (SA). This will mean that
> civilian users of GPS will be able to pinpoint locations up to ten times
> more accurately than they do now. GPS is a dual-use, satellite-based
> system that provides accurate location and timing data to users worldwide.
> My March 1996 Presidential Decision Directive included in the goals for GPS
> to: ?encourage acceptance and integration of GPS into peaceful civil,
> commercial and scientific applications worldwide; and to encourage private
> sector investment in and use of U.S. GPS technologies and services.? To
> meet these goals, I committed the U.S. to discontinuing the use of SA by
> 2006 with an annual assessment of its continued use beginning this year.
>
> The decision to discontinue SA is the latest measure in an on-going effort
> to make GPS more responsive to civil and commercial users worldwide. Last
> year, Vice President Gore announced our plans to modernize GPS by adding
> two new civilian signals to enhance the civil and commercial service. This
> initiative is on-track and the budget further advances modernization by
> incorporating some of the new features on up to 18 additional satellites
> that are already awaiting launch or are in production. We will continue to
> provide all of these capabilities to worldwide users free of charge.
>
> My decision to discontinue SA was based upon a recommendation by the
> Secretary of Defense in coordination with the Departments of State,
> Transportation, Commerce, the Director of Central Intelligence, and other
> Executive Branch Departments and Agencies. They realized that worldwide
> transportation safety, scientific, and commercial interests could best be
> served by discontinuation of SA. Along with our commitment to enhance GPS
> for peaceful applications, my administration is committed to preserving
> fully the military utility of GPS. The decision to discontinue SA is
> coupled with our continuing efforts to upgrade the military utility of our
> systems that use GPS, and is supported by threat assessments which conclude
> that setting SA to zero at this time would have minimal impact on national
> security. Additionally, we have demonstrated the capability to selectively
> deny GPS signals on a regional basis when our national security is
> threatened. This regional approach to denying navigation services is
> consistent with the 1996 plan to discontinue the degradation of civil and
> commercial GPS service globally through the SA technique.
>
> Originally developed by the Department of Defense as a military system, GPS
> has become a global utility. It benefits users around the world in many
> different applications, including air, road, marine, and rail navigation,
> telecommunications, emergency response, oil exploration, mining, and many
> more. Civilian users will realize a dramatic improvement in GPS accuracy
> with the discontinuation of SA. For example, emergency teams responding to
> a cry for help can now determine what side of the highway they must respond
> to, thereby saving precious minutes. This increase in accuracy will allow
> new GPS applications to emerge and continue to enhance the lives of people
> around the world.
>
>
--
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Paul Taylor Veni, vidi, tici -
I came, I saw, I ticked.
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