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Features October 2019 Issue

Why GPS Doesn’t Work

This is the ADS-B-reported track received by ATC from a Citation at FL310 using VOR navigation during deliberate GPS interference testing. Clearly, this is unsuitable for ATC purposes. The colored contour lines represent expected areas of GPS interference. (The poor quality image was from the source, an RTCA document.)

Why GPS Doesn’t Work

In the post 9/11 world, security is clashing with utility and aviation is on the front lines, with consistent and reliable GPS signals at the center of the conflict.

Dark clouds are looming on the horizon of our otherwise exciting GPS future. With increasing frequency, the military is jamming or spoofing GPS over huge swaths of airspace. A typical GPS NOTAM for Albuquerque center covers a radius of 237 NM at 10,000 feet, 207 NM at 400 feet and 165 NM at 50 feet daily for most of a week. Pilots in the Southwest have become accustomed to these NOTAMs, but they’re becoming more frequent and expanding to other areas of the country.

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