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In the February issue of PMY, editor-in-chief Richard Thiel cautioned readers to always navigate with a pencil-on-chart backup plan because GPS–in fact any electronic device–is inherently susceptible to failure. Frankly, I was a wee bit skeptical. While I’ve regularly heard old salts like the chief expressing wary views of high-tech ways around the bridge, I’ve personally experienced a high degree of GPS reliability, not to mention the splendid operating features of GPS-driven chartplotters and PC nav programs.

Nonetheless, with more references to "GPS vulnerability" cropping up in the press, I decided to do some deeper research. I’ve now actually read the 113-page Vulnerability Assessment of the Transportation Infrastructure Relying on the Global Positioning System, also known as the Volpe Report, after the government research center that compiled its dry text. In addition, I spoke at length with a gentleman named Langhorne Bond, who retired from public service in the transportation sector–including a stint as Administrator of the FAA–only to spend the last five years shouting from lonely rooftops about the dangers of over-dependence on GPS. I surfaced with an entirely new attitude. It appears that the satellites seduced a great many of us, from top government regulators on down; and it’s time to get real.

When the U.S. military released a GPS frequency for civilian use in 1990, no one anticipated how rapidly it would turn into a widespread technological religion. Soon I was packing my adored handheld on yacht deliveries and, like many of my brethren, thought the evolution to constant plotting on digital charts was the greatest advancement in navigation since radar. In 1994 the Coast Guard announced that Loran, the previous somewhat cranky method of electronic navigation, would be phased out in 2001. Foreign stations were turned over to host countries, and the market for Loran pretty much vanished.

Aviation authorities also began to see GPS as a total electronic navigation solution. Both the Coast Guard and FAA started working on their own "differential" systems to overcome the Selective Availability (SA) inaccuracy mandated on civilian GPS to prevent enemies from using it for targeting. In fact, about this time last year, the big GPS issue for us marine electronics pundits was the relative merits of the FAA’s WAAS versus the Coast Guard’s DGPS. How naive we were. Both have value for intensely precise navigation, but the truth is that when SA was rather suddenly turned off in 2000, GPS became sufficiently accurate for most pleasure boaters.

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