Sailing The World, One Chart At A Time
Throughout the long, complicated history of the map, it’s gone through several iterations with different duties. While often seen or relegated to little more than a piece of unnecessary classroom décor or a basic tool for memorizing the world’s countries these days, it’s historically played a huge part in travel and exploration, particularly at sea. And this is all thanks to nautical charts.
Of course, these charts are only as helpful as one’s ability to read them, which can pose a problem for most typical people out there. Consider yourself part of these ranks? Well, you don’t need to stay that way. All you need is a touch of guidance, and you can read these charts in no time. Read on, and we’ll explain all the basics of plotting and what you need to understand these navigational charts today.
What Is A Nautical Chart
First, let’s clarify precisely what a nautical chart is in the first place. A nautical chart is a visual representation that displays the details of various hydrographic data. It essentially acts as a practical “roadmap” of our waterways, relaying critical data about water depths, shape of the coast and shoreline, locations of islands and important “landmarks” or navigation markers, potential hazards/obstructions to ships, bridge heights, latitude and longitude scales, tide predictions, navigational aid, and more.
In other words, nautical charts contain amazing amounts of information that anyone operating a ship or boat should know. They’re a wonderful aid to keep you safe and sound in the figuratively (or sometimes literally) choppy waters and are essentials for any vessel that’s venturing away from land. Pretty simple stuff at the core, right? However, nautical charts aren’t one-size-fits-all. There are a few common types to choose from, including general, sailing, harbor, and shore charts that differ by their particular scale and specific use cases.
Luckily, their self-explanatory type names make choosing what’ll work best for you rather simple. You’ll still need to acquire one in the location you’re traversing, though, within a format you can readily interpret. Head on over to the navigational chart page, and we should have just the ticket, carrying charts from both the US National Oceanic and Atmospheric Administration and the National Geospatial Intelligence Agency to ensure we’ve got everything you need and more.
How To Use a Nautical Chart
Reading and using nautical navigation charts is crazy intimidating at first glance. Admittedly, they look crazy. There’s a lot to interpret, and it’s liable to trip you up as a beginner, but it doesn’t have to. A little preparation, a few steps, and you’ll be reading them like a champ.
The first step here is to simply familiarize yourself with the layout of your chart. Just take it all in for a moment. That’ll eliminate some of that haze or overwhelmed feeling people sometimes get when viewing tons of new information at once. Then, you can start to look for the individual pieces of information that’ll prepare you for your journey. Here’s a quick breakdown to help you out:
- Scale. Somewhere on your map, you’ll see a number expressed as a ratio (ex. 1:100,000). This is your scale and will help you track distances on your map. In the case of our example, this means that every one inch on the map translates to 100,000 IRL.
- Water depth. It’s crucial for any navigator to know the water’s lowest depth measurements, although nautical charts can make this a little complicated. To find this value, consult the chart that displays depth. The printed numbers in the boxes represent the average depth during low tide. Confused because you see a negative number? That means the depth is actually lower than the listed value most of the time, so beware! Otherwise, water levels are generally higher than listed. Also, be sure to pay attention to the unit of measurement. Meters are pretty common these days, but feet and fathoms are still around – and you don’t want to get these mixed up. So, look near the scale to find the unit before trying to interpret anything on your chart.
- Contour lines. Contour lines – those dotted lines on your chart – give guidance about happenings below the water’s surface. Red lines will show where water is relatively stable, similar in-depth, and effectively split oceans, lakes, etc., into areas of deeper and shallower water. Lighter areas are usually coded as a light blue, and yellow, tan, or beige indicate sandbars.
- Navigational guides. Nautical charts are meant to aid in navigation and use several methods to do so. The compass rose is one of them, identifying the direction you’re traveling. Red and green markers symbolize buoys, with the former always on a channel’s right side and the latter on the left. Keep track of this, and you’ll always be able to orient yourself. Meanwhile, arrows demonstrate the typical direction and speed of tides or currents, letting you know the best direction to not fight the water and traverse safely.
- Docking. Like with cars, you’ll need to stop at some point, and maps help there, too. You’ll find anchor symbols interspersed throughout your chart. These are places you can safely anchor, often labeled with numbers, descriptions, or abbreviations to let you know what kind of ships are allowed and for how long.
- Hazards and obstructions. Hazards and various dangers are a natural part of water travel, and nautical charts make sure to alert you to these right off the bat. To find them, look for circled areas on the map. These typically show things like shipwrecks, problematic rocks, and other things that could pose harm to a ship and its persons.
The Basics of Plotting
Anytime you’re setting out on the boat, being able to read your nautical charts is half the battle. But you also need the ability to plot your course. Worried you’ll get it wrong? Don’t be. It’s not nearly as rough as you might imagine. We’ll walk you through the basics.
First thing’s first: a few tools will need to be gathered. For our purposes, this’ll include your nautical chart of choice, parallel plotters, dividers, a pencil, and a stopwatch. Once you’ve got these at the ready, follow these easy steps, and you’ll be on your way.
- Pull out your parallel plotters and draw a straight line from where you’re departing to your destination. Feel free to draw as many of these as you need to represent your entire trip.
- Use an edge of your parallel rulers and lay it down on the line you drew. Roll it to the closest compass rose available on your chart, making sure to stop as it intersects the central point’s crossed lines.
- Read where the course line intersects with the inner degree circle. This is your magnetic bearing. Once you find this, jot it down above your line and continue to do this until you’ve finished it up for every course line drawn earlier.
- Use your dividers and scale to determine the distance of each course line and record these below everyone.
- Take a look at your average knot speed and take into account the different conditions for your course lines. Note these by your bearing and continue to calculate the time needed to run your courses by taking your distance and multiplying it. Use this value and divide by predetermined speed. You should then get the minutes and seconds needed for your course time. Once again, repeat this for everything and write it down at the bottom of your course lines.
- Finally, take your stopwatch and run the course you plotted! Make sure to point your boat in the direction charted and use the speed you calculated. As each course time passes, continue to restart the watch, pay attention to your time, and continuously reorient yourself on the created path. Do this, and you should get exactly where you wanted to be.
