[jamsat-bb:5267] GPS SA 解除！！！

[Kohjin Yamada <kohjin@marina.prug.or.jp>]

只今０９：００UTC報じられた通りGPSのSAが解除されました。
（本日付け朝日新聞夕刊及び以下の資料をご覧下さい）

今までSAがあった時には高度が数百メートルも上下していましたのが
１メートル以内に収まっています。

TAC32で見ています。

山田 − JR1EDE

=========================from tacgps=======================
Date: Mon, 01 May 2000 16:18:38 +0000
From: Dr Thomas A Clark <clark@tomcat.gsfc.nasa.gov>
Organization: NASA/GSFC
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To: TAPR APRS SIG <aprssig@lists.tapr.org>, AMSAT BB <amsat-bb@AMSAT.Org>
Subject: GPS S/A To Be Turned Off
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The White House released this press release today -- S/A est morte !


---------------------------------------------------------------------


[available at http://www.whitehouse.gov/library/PressReleases.cgi]



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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