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    A GPS story
    From: Frank Reed
    Date: 2012 Jul 12, 12:27 -0700

    Alan, you wrote:
    "1. Notwithstanding GPS, learning what you dismiss might well turn out to be an interesting intellectual exercise, notwithstanding the fact that GPS units, I too have one, have been known to fail, no?"

    I think all of us here recognize that the expression "GPS unit" has two meanings. Every vessel today with any intention of sailing out of sight of land has a GPS system meaning a computer loaded with electronic charts of various types and position fixed by GPS input. I say "every" and it is almost without exception --even "traditional" dhows sailing across the northern Indian ocean carry GPS systems for their navigation. Somali pirates use GPS systems. Most ocean-going vessels also have available a much simpler GPS receiver, or several, as a backup. This could be as basic as a cell phone or even a ten-year-old handheld Garmin unit. The best backup for a GPS is another GPS, meaning that the best backup for a complete GPS system is that basic, handheld GPS receiver. Anyone who goes to sea WITH a GPS system and WITHOUT a backup GPS is just an idiot.

    The difference, of course, between a complete "GPS system" and a handheld GPS is that the smaller unit does not necessarily include all the plotting functions and other chart "intelligence" (though it may). So the navigator with a failed GPS system requires one basic traditional skill --chart plotting. You would be amazed how rare this skill is even in the world's navies. A fried of mine in Chicago recently told me a "failed electronics" story. He was in bad weather on Lake Michigan, and all the electronics failed, most importantly the GPS plotting system and the radar. And as he explained to me rather proudly, he fell back on "old fashioned" tools. When I asked for details, imagining him taking compass bearings, it turned out that he meant he had to pull out a paper chart and figure out how to plot latitude and longitude on it. He had a backup GPS unit for his position fix. That's what he meant by "old fashioned". It was a simple GPS receiver from ten years ago.

    There was another "GPS" story recently here locally in which a woman claimed that her car had ended up in a bunker (sand trap) on a golf course because her GPS told her to turn there. And that's how the tv news prefaced the story: "her GPS did it". The story concluded "police charged her with DUI and found that she was well over the legal alcohol limit". Yeah, that makes more sense.

    There is another way that GPS can fail. The entire network might be hit by some problem. As little as a year ago this was still a small window for some concern --a good reason to have a non-GPS backup. But the Russian Glonass system is now back online as of about nine months ago after over a decade when replacement satellites were not funded (the Russian aerospace industry had traditionally built satellites with short lifespans under the assumption that it was cheaper to build simple and launch often). A navigator who worries about failure of the entire US GPS network can easily purchase a Glonass-capable system. In just a few years the European and Chinese satellite navigation networks will also be available. There are still natural space weather events and man-made jamming that could affect ALL of the systems, but the odds are much smaller now.

    Celestial navigation is a backup for a backup that will almost certainly never be used. Despite its limited practical value, celestial navigation is still required by many international regulations and still occasionally "practiced" by the mariners of many navies. And hell, it's good, clean fun. That's good enough for me.

    -FER


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