Which is Quicker and More Accurate: GPS or Compass?
Brought to you by coastalnavigation.com
The GPS is a neat little piece of electronics that is almost as reliable as your compass. What you say? Well, consider these facts: The GPS may be accurate in giving your boat's position, but sometimes there are problems. Its signal can be shut off by the US government without warning, it may be more accurate than the chart you're using, it may fall overboard (with or without you), and its batteries may go dead or power source dry up. And you could be aground while the chart shows you in the middle of the channel - if the chart was sounded inaccurately, which can happen.
Your non-electronic compass is always on, needs no batteries and always points to magnetic north, giving you instant awareness of which direction your boat and you are heading. If you know the local variation and your deviation, it's more reliable and quicker to use for a fix than a GPS. Think of sitting in the cockpit, the chart and plotter on your lap, you whisk up the hand-held compass or peer over the boat's compass at a landmark. In 30 seconds you can have two lines of position about 60° apart and, after a quick calculation for variation and deviation, have plotted them in another half minute, and there's your fix. Right there, where the little lines cross on your chart. Now you know where you are, where the rocks are, and which way is home. Total time? Under a minute, two at the most.
Now, turn on your GPS (silent buzzes and whirrs) wait a minute or more to get it going. And figure another 30 seconds for it to find three satellites to triangulate your position. Then you have to press the RIGHT buttons, and in another few seconds, you should have an accurate read out of your latitude and longitude. But now you have to plot the position. So, get out your dividers (did you leave them below?), measure the lat on the side of the chart, make a small pencil mark, do the same for longitude - another pencil mark, make the lines cross, and there you are, another fix with little crossed lines after two minutes of precision work. Total time? Probably about three or four minutes or more.
But what about accuracy? With GPS, and with the US government co-operating, with Selective Availability (the accuracy-fudging mechanism to thwart terrorists) turned off, with the proper up-to-date chart and with WAAS or differential corrections operating properly, there's NO DOUBT your GPS position will tell you within an impressive 10 metres or so, exactly where the GPS unit is. You can't do that with a compass, although in quiet waters and ideal conditions of clearly charted landmarks you can come close. So where does this leave you?
Well, there are a lot of "ifs" regarding GPS, and there's the matter of properly correcting from your compass reading to true, so you can plot it on the chart with confidence. On balance, it's fair to say both can work well if all the conditions for GPS are met and if you are comfortable with correcting the compass.
coastalnavigation.com's on-line course teaches the working of the compass,
and its instructors are well versed in the uses and practicalities of using
GPS. In brief, we'd recommend you have these tools, the more important being
the workings of the compass. That's because you need that knowledge to understand
and apply the intricacies of using the GPS. We teach that. The CYA Standard
is a high standard recognized around the world so you can charter a boat in
the Caribbean or Greece or anywhere. The charter operator would really like
to know if you understand a few things about getting where you want to go,
and safely too. The CYA Standard presented by the on-line course, coastalnavigation.com,
gets you there, and safely too.
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