I'm looking for an inexpensive knotmeter for my Flying Scot. Is it possible to use some GPS units to measure speed?
Dan Dickison responds:
It's interesting that you should ask that question right now because currently there's a heated debate going on within SailNet's racing list on this very topic. (By the way, should you like to participate, see the instructions below.)
Yes, you can use a handheld or stationary GPS unit to gauge your boat's speed, and the most recent units are quite accurate. But be advised that most GPS units register speed over the ground, not through the water. If you were cruising and wanted to use a GPS to determine boat speed for navigation, that would be fine. However, since you've got a Flying Scot, I'm going to assume that you're probably more of a daysailor or a racer, and I supspect that you'd want speed data for the purposes of indicating your performance. If so, you'd be better off with instruments that are not only accurate in a geographic sense, but also offer an indication of speed through the water. That way you'll have a good idea of whether you're accelerating or decelerating.
There are a couple of other products that can help you determine the speed of your boat. Among them I recommend Speedmate's Knotmeter. To buy this you'd spend about the same amount of money for a reliable handheld GPS unit, but you wouldn't get instant feedback on fluctuations in boat speed. I hope this information helps you make up your mind.
Now, if you'd like to get in on that discussion I mentioned, just log on to SailNet's homepage and click on "Join E-Mail Lists," which is located under the heading "Members." That will take you to an index page where the e-mail discussion lists (we support almost 200 of them) are listed by geographic area and boat type. Best of luck to you.