Getting from point A to point B without running into anything above or below the water. That’s the essence of navigation. It’s all about figuring out where you are, where you want to go, how to get there, and what obstacles to avoid.

Aids to Navigation

Visual markings on the water and along the coast such as buoys and waterway mark are known as aids to navigation or ATONs. They come in all shapes and sizes and are most useful simply as unique position identifiers when trying to locate your location on a chart. Also of importance are regulatory markings indicating top speed and other restrictions in channels or marinas.

The appendix contains Coast Guard summary charts of the ATONs used in the US, including their corresponding chart markings. For a more complete explanation, see the Coast Guard reference at:

http://www.uscgboating.org/assets/1/workflow_staging/Publications/486.PDF

Red Right Returning

It can be confusing deciphering the specific meaning of an ATON, but fortunately, the most important information – which side you should be on – is easy to figure out.

Markings that direct you to pass on one side or the other will be either red or green. They are used to prevent boats from running aground or hitting an underwater obstruction. Most ATONs you’ll see will be red or green or will be marina markings regulating speed, wake, etc. To figure out which side of a colored marking you should pass on, there is a simple system called Red Right Returning.

Here’s how it works. When returning from the open sea to a marina or channel (or going up stream when you’re on a river), you keep red markings, on your right (i.e., starboard).

You may be thinking, “That’s great, but what if I’m not returning?” Well the nice thing about Red Right Returning is that it works kind of like a math equality. If you change any one of the words, you then have to change another one (only one) to get it to “balance.”

For example, if you are leaving instead of returning, you would then have to change either red to green or right to left. So you could have either Red Left Leaving, or Green Right Leaving. You can then make sure to either have a red marker on you right or a green marker on your left. Whether you’re leaving or returning, or whether you see a red or green marker, you can use Red Right Returning to determine which side to pass on.

Just remember that the direction, right, means that you have to have the marker on your right, NOT that you should pass to the right side of the marker.

You can also use Red Right Returning to deduce information about the waterway you’re on. Sometimes it’s obvious which side of a marker you should pass on because there’s a bank or other land formation on the opposite side. In that case, you can use Red Right Returning to determine what direction is considered “Returning” for the particular waterway you’re on if there’s any ambiguity.

If you happen to be color blind or for some reason the color of the marking is unclear, you can use the numbers as an alternative. Red markings should have even numbers, and green markings should have odd numbers. Also note that the numbers on colored markings should be increase as you progress inland, which is considered the “Returning” direction.

Navigation

Navigation – figuring out where you are and how to get where you want to go – has been greatly simplified with modern technology. GPS systems are widely available in both handheld portable units or as built in onboard instrumentation and require almost no nautical knowledge to use.

Most recreational sailors don’t need to pinpoint exact location anyway, but if you ever do want to sail further into the unknown, it helps to have a basic understanding of traditional navigation or charting. I won’t go into too much detail – there are many resources available for those who wish to become navigation experts – but I’ll just explain the basic concepts.

Essentially, charting involves using visible landmarks to figure out a boat’s location. It’s all simple geometry, but does require some thorough bookkeeping. There are also other complications like correcting your boat’s compass (a magnet) depending on where on Earth you’re located.

Geometrically, you need only two reference points to identify the location of your boat (more points improve accuracy). After finding the angle between each point and the boat using a compass, you draw a line from each know reference point on a nautical chart (i.e., a map) and the intersection of those lines is your boat’s location. You now have a fix, or an estimate of your boat’s location at a specific time.

By keeping track of your speed, heading, and the amount of time that has passed since your last fix, you can estimate your path through the water. This process is known as dead reckoning.

You can easily estimate a course using a nautical chart and your boat speed in knots. As discussed earlier, a knot is simply a nautical mile – or one minute of latitude – per hour. The fact that nautical maps are marked in longitude and latitude makes this process very simple. Of course, a complicating factor is the difference between longitude and latitude. While surface distance between latitude lines constant everywhere on Earth, longitude lines converge at the poles. Precise charting takes this into account.

In summary, charting is a very simple idea – triangulating a position and extrapolating using speed and direction – but gets complicated when you take into account all the slight adjustments and that need to be made. You’re much better off using the GPS if you can.