GPS Accuracy Increases Dramatically 2
Author thumbnail By M. Scott Smith, DCSki Editor

On May 1, President Clinton made a surprise announcement that the United States would immediately discontinue the intentional degradation of Global Positioning System (GPS) signals, six years ahead of schedule. At midnight on May 1, Selective Availability - the intentional degradation of civilian GPS signals - was turned off and all consumer GPS receivers immediately realized a significant gain in accuracy.

“In plain English, we are unscrambling the GPS signal,” explained Presidential Science Advisor Neal Lane during a press conference on May 1.

“It’s rare that someone can press a button and make something you own instantly more valuable, but that’s exactly what’s going to happen today. All the people who bought a GPS receiver for a boat or a car, or their riding lawn mower or whatever, to use in business and in recreation, are going to find that they’re suddenly 10 times more accurate as of midnight tonight,” Lane said.

On May 2, civilian GPS receivers increased in accuracy, and now should see an error rate of 20 meters or less, improving their utility in a wide range of applications.

GPS was developed by the U.S. military to provide pinpoint navigational accuracy, using a network of 24 satellites transmitting signals and ground-based receivers that triangulate on the signals to produce latitude and longitude readings anywhere on earth.

GPS has served a dual-purpose role, concurrently supporting both military and consumer/business applications. To address these dual roles, GPS incorporated a feature known as Selective Availability (SA) that intentionally introduced errors into its signals, decreasing accuracy for non-military receivers. The government planned to eliminate SA by 2006 after introducing techniques that allow regional degradation of GPS signals during conflicts, but successfully demonstrated these new techniques earlier this year.

“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,” said President Clinton in a statement. “They realized that worldwide transportation safety, scientific, and commercial interests could best be served by discontinuation of SA.”

GPS receivers - once an expensive gadget - have recently dropped in price and found a broad range of applications. There are now more than 4 million GPS users worldwide, and the $8 billion industry is expected to double in the next three years. GPS technology is used in air, road, rail and marine navigation, and may be incorporated into next-generation cell phones to provide location for emergency response calls. GPS satellites include on-board atomic clocks, and many earth-based devices (such as ATM machines) rely on clock signals from GPS satellites for extremely sensitive timing.

Skiers, hikers, and mountain bikers will immediately benefit from the increased accuracy of GPS receivers, navigating through unmarked wilderness terrain with increased confidence and safety. The accuracy of GPS now exceeds the resolution of U.S. Geological Survey topographical quad maps.

About M. Scott Smith

M. Scott Smith is the founder and Editor of DCSki. Scott loves outdoor activities such as camping, hiking, kayaking, skiing, and mountain biking. He is an avid photographer and writer.

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Reader Comments

July 26, 2000
I deal with export control matters, some pertaining to GPS. My coworkers and I found this article illuminating.
Philip G
March 12, 2001
Great information for the introduction
to GPS. The SA information should be updated.

Ski and Tell

Speak truth to powder.

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