Tools for Navigation in Coastal Waters

Good tools are required for chartwork, which in turn is essential for accurate navigation. In these days of electronic chartplotters and GPS, many people think that traditional charts are passe. That could not be farther from the truth. Although we embrace electronics wholeheartedly, we have also experienced complete electrical failure onboard two different vessels for a total of three times. One for failure of batteries to hold a charge while offshore, the second as a result of lightning discharge, and the third with failure of our alternator. In each of those cases, it was beyond our control, and we were more than ecstatic about knowing our position and being able to resort to backup paper with the time of our last known position, course made good and speed clearly marked.

We make it routine habit to mark our charts on longer distance passages every hour at least, just in case. That way, we also can tell whether our GPS waypoints will deliver us to our expected destination. There are many stories about sailors who entered a coordinate, turned on the autopilot, and ended up on an island that was between two waypoints. Had they looked at a chart as backup reference, they might have noticed the slight obstacle and saved themselves an embarrasing and potentially very costly proposition.

If you haven't taken a basic navigation class, you probably should and the USCG Auxiliary does a fine job in their local advanced navigation courses. Similarly US Sailing offers certification programs. Getting started is not that difficult and there are many resources both online and in your bookstore. The first place to start is with some basic plotting tools.

1. Parallel Rulers and Rolling Rulers are used to transfer bearings from the compass rose on the chart to the location of the course being plotted or for determining a position on the chart. 

2. A Chart Plotter is a sheet of plastic onto which a compass rose is printed. Attached to the center of the compass rose is an arm or a string. By placing the centre of the compass rose over the location you are presently at and extending the string or arm to your destination, the bearing of the course required can be read off the plotter. The chart plotter is quick and effective for recreational navigation and helps maintain the life of the chart by removing the need to draw on it. Some give true readings, others are adjusted for local variation.

A simple and cheap chart plotter can be made using a 360° protractor with a small hole drilled in the centre. Crocheting yarn or similar material threaded through the hole with a knot on the underside can act as the bearing finder.

3. Dividers and compass are used for calculating distances. The distance is measured on the chart with the dividers and then compared to the scale of the chart. Keep in mind that you don't need to find a scale notation. One minute of latitude equals one nautical mile, so every chart has its own scale built into the grid on the edge.  A compass has lead in one side which allows you to mark off positions from multiple bearings and where they intersect is your fixed position.

A simple alternative to dividers is a clean straight edge, such as a sheet of paper. Mark the distance between the two locations on the paper, then read it against the side scale for comparison and calculation of the distance.

4. Pencil and eraser are as much tools of the trade as anything else. I like mechanical pencils and art erasers, which do not mar the charts if you wish to erase a route when you're done.

5. Chart Number One is used to interpret a chart. It tells what all the abreviations and symbols mean. Without it you wouldn't know that "s" is soft and "S" is sand, but it's amazing how few people know about this great resource and how many fewer actually have one onboard. You should have one whether you rely on electronic or paper charts. And, you can download it for free (along with the Coast Pilot, Bowditch and countless other resources) or purchase it as a book for about $10.

6. Calculators are a great way to check your figures. We have a small battery powered one that works on solar as well. I can't tell you how many times I've found serious errors in my calculations just by doing them twice.

7. Speed/distance wheel is a simple tool for solving S=d/t without performing any calculations.

Speed = distance / time

8. Tide tables current for your year and location are indispensible.

9. Coast pilotwhich provides all the information you need about approaches to harbors, including lights and chartlets, is now available free online updated with current Notices to Mariners or purchased as an annual edition, often in combination with tide tables for the year (e.g. Reed's, Eldridge's)

10. Rules of the Road is the publication that tells you who had the right of way according to most situations of encounter on the water. These rules are required to be onboard any vessel in US waters that is longer than 12 meters (39 feet). You can order a copy from the government for about $15 or you can download them for free online. The online site also includes self-tests and many resources for learning the rules and applying them.

Now you put these all to good use!

More Reading: GPS and Nautical Charts

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