Sailors beware

Navigation has gone high-tech. A gadget that can tune in on the Global Positioning System (GPS) and use satellites to tell your latitude and longitude is getting cheaper and better. It used to cost thousands of dollars, but hand-held models now sell for less than $200. Until last year, the federal government, as a security measure, put in an automatic error, which meant that your instrument might be as much as 100 feet off. Now the government has stopped that practice, and the error is only about 30 feet.

This year, fishermen and yachtsmen can reduce the likely error to 10 feet, according to Boat/US Magazine, by using either something called GPS with Differential or else the Wide Area Augmentation System, known as WAAS, which was originally designed for airplane pilots. As a practical matter, most sailors will not need these refinements the way a pilot would when landing in a fog.

But the same issue of Boat/US Magazine warns that the electronic charts in most of these gadgets are merely copies of the standard government paper charts. And some of the paper charts reflect surveys that are decades old. Wrecks and other hazards may not yet be charted. Water depths may be inaccurate. Numbers and positions of buoys may have been changed.

The lesson from these reports is an old one, but it bears repeating: Rely first on your own observation, watching and recording course and speed, and keeping a good lookout. Use the electronics only as a backup.