New GPS Accuracy: The Real Story

By Heather Siladi

Published on May 20, 2006

Until recently, the government has actually been scrambling GPS signals through a process called selective availability (SA). This process altered the GPS signals received by civilian users, which made positioning only accurate to within 100 meters. The United States military has always had access to the unscrambled signals which are accurate to within 20 or 30 meters.

GPS works by coordinating the position of an object which is being detected by several satellites at the same time. SA works by scrambling the clock readings from the satellites which in turn decreases the accuracy of the GPS reading from within 30 meters to within 100 meters.

This "unscrambling" is being praised as a huge step forward, particularly for rescue aviation safety and rescue operations.

Although this appears to be a big step forward, the fact is that unscrambled GPS data has always been available for a price, through companies that could correct for the satellite clock signal deficiencies.

Many experts speculate that the government’s decision to no longer scramble GPS reading must be a sign that they have found a new, secret way to overcome enemy GPS readings.

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