Clinton lifts GPS blinders
- By Paula Shaki Trimble
- May 08, 2000
A White House decision last week to take the Pentagon-imposed blinders off
the Global Positioning System will lead to faster, better and cheaper government
services, according to federal officials.
President Clinton on May 1 delivered on a 4-year-old promise to improve
the accuracy of the satellite navigation system for civilian users by deactivating
a feature that intentionally skewed GPS positioning and timing data sent
to civilian receivers.
The feature, known as selective availability, was intended to prevent
hostile forces from using GPS positioning information in strikes against
the United States. But the Pentagon has concluded such a feature is no longer
Selective availability was set to zero at midnight May 1, with GPS satellite
operators commanding the satellites to stop distorting the signal transmitted
to civilian users, said Neal Lane, the president's science adviser, during
a press briefing earlier in the day.
"It's rare that you can press a button and make something you already
own instantly more valuable," Lane said.
At the Commerce Department's National Oceanic and Atmospheric Administration,
James Baker foresees speedy delivery of weather predictions and evaluations
from less expensive future weather satellites.
The improved accuracy of GPS will require less data processing of positioning
and timing information received by NOAA weather satellites. Because weather
satellites will no longer have to be equipped with all the instruments needed
to correct GPS data, the cost of a satellite launch, which is calculated
per pound, will be lower, said Baker, undersecretary of commerce for oceans
and atmosphere and NOAA's administrator.
"This is only the tip of the iceberg for improvements to the GPS system,"
Baker said. The Defense Department plans to provide civilian GPS users with
a second satellite signal as part of satellites scheduled for launch beginning
in 2003, and with a third signal starting in 2005.
The additional satellite signals will provide much-needed redundancy,
like the second engine on an airplane. People using GPS for life-and-death
applications cannot afford to have the signal suddenly disappear. The additional
signals will allow GPS to overcome the natural interference that occurs
when the satellite signal passes through the ionosphere.
GPS is a system of at least 24 orbiting satellites — there are now 27 — operated by DOD that provides accurate positioning and timing information
to users on the ground, in the air or in space. GPS is used to guide missiles,
navigate civilian aircraft and synchronize cellular and digital telecommunications
In a presidential directive in 1996, Clinton promised to annually revisit
the issue of intentionally degrading the civilian GPS signal beginning in
The White House decided to deactivate selective availability now because
DOD has sufficiently proved its ability to deny the GPS signal to adversaries
in a specific region while maintaining availability to users elsewhere,
said Arthur Money, assistant secretary of defense for command, control,
communications and intelligence.
DOD would not agree to shut off selective availability until it had
developed and tested technology that protects the advantage of the warfighter
in a conflict area, Money said.
Although the modification significantly improves the accuracy of the
GPS signal, the Transportation Department is still committed to developing
systems that augment GPS capability, said Eugene Conti, assistant secretary
of transportation for transportation policy.
Those systems, such as the Federal Aviation Administration's Wide-Area
and Local-Area augmentation systems and the Coast Guard's National Differential
GPS, verify that the GPS signal is reliable and improve accuracy even more.
U.S. officials will continue discussions with their counterparts in
Europe about the European Union's plans to develop another satellite navigation
system called Galileo that could be interoperable with GPS, said Jeffrey
Bialos, head of the U.S. delegation for discussions with the EU. "This decision
means we have a more robust and precise GPS than before," he said. How that
will affect the European strategy remains to be seen, he said.