Learning how to navigate a boat is one of the most important things any boat owner must learn. Essentially, nautical navigation is no more than knowing how to get from Point A to Point B. But the process can be a whole lot more challenging than simply pointing the bow in the right direction.
Everyone, of course, is more or less familiar with some form of navigation. It’s what you do every time you travel, whether you’re jogging through a park or driving into town. But on the water, navigation takes on a new level of complexity. First off, there are no roads to follow. Secondly, visibility may be restricted by fog, rain, haze, and darkness. And thirdly, paths that appear to be safe to the naked eye may in fact be filled with hards such as shallow zones, underwater obstructions, piers or pilings, commercial fishing gear, and more. So, how will you navigate through these treacherous waters? We’ll take a close look at two methods: traditional navigation and electronic navigation.
Just a few short decades ago we didn’t have electronics like GPS and chartplotters. And going back for thousands of years, mariners have been studying how to safely get across rivers, bays, and oceans. No matter where you’re navigating or what type of boat you’re on, the number-one tool you use while navigating is your own eyes. Beyond that, standard navigation tools include:
- A compass and/or hand bearing compass: A compass tells you which direction your boat is heading in, north, south, east, or west, as measured in degrees relative to magnetic north. There are 360 degrees representing a full circle, with 0 degrees to the north, 180 degrees to the south, 90 degrees to the east, and 270 degrees to the west. A hand-bearing compass can be utilized to quickly take multiple “bearings” (the direction of a course, or the direction to an item or place) of multiple visible landmarks.
- Charts: Charts are nautical maps. NOAA (the National Oceanic and Atmospheric Association) produces charts of navigable US waterways, as well as many international charts. You can buy NOAA charts or view them online for free.
- Parallel Rules: These are a set of two rulers which are attached by swiveling arms. The arms allow you to open and close the rulers, “walking” them across a chart, while maintaining the same angle.
- Dividers: This tool (also sometimes called “compass dividers”) is used to measure distance on a chart. You can separate its two points more or less, to represent a nautical mile or a number of miles.
- An erasable pencil: A pencil is needed for navigation via chart so you can mark down important items like speed, location, and bearings.
- A wristwatch or stopwatch: In order to perform one of the most basic forms of navigation—ded reckoning (or "deduced reckoning"), which we’ll talk more about in a moment—you need to keep track of time.
Some calculations can be made more easily with items like a nautical slide rule or a protractor, but the above list covers the absolute necessities for basic nautical navigation.
So, just how do you use these tools while getting from Point A to Point B? Here are some of the basic things you’ll need to do to navigate your boat:
- Locate your position
- Create a route with bearings
- Determine a reciprocal course
- Plot your position with Ded Reckoning
Locating Your Position: Sometimes you can simply look at your surroundings, glance at the chart, and you’ll know where you are. Say for example that you’re next to a big red buoy with the number five on it, and when you look on the chart you see the red number five buoy front and center. Position acquired. But locating your position may be easier said than done, especially in unfamiliar waters. One of the most basic (and best) ways to accomplish this feat is triangulation. In order to triangulate your position you’ll need to identify three visible landmarks or aids to navigation that are clearly marked on your chart, and are relatively far apart from each other (the farther, the more accurate your calculation will be). Lighthouses, points of land, water or radio towers, and navigational markers are prime examples.
First, use your hand-bearing compass to “shoot” a bearing to the first landmark (or, if you only have the compass mounted at your helm, point the entire boat directly at it to acquire the bearing). Line up your parallel rules on the chart’s compass rose (the illustrated circle marked with degrees) to match the degree of the bearing you shot. Note that there are two circles of degrees on the rose, one (the outer ring) representing true north and the other (the inner ring) representing magnetic north. Use the inner magnetic ring, because your compass points to magnetic north, not true north. Then, walk the rules across the chart by holding down one side and moving the other towards your landmark, one after the other. When an edge of your parallel rule intersects with the landmark, use your pencil to trace a line down the rule’s edge.
Now, repeat the process with the other two landmarks. If the three lines you’ve drawn intersect, you now know exactly where you are on the chart. If they come close and create a triangle, you’re somewhere inside that triangle. You can get a more exact location by adding more landmarks and bearings, or by taking more accurate bearings.
Watch our Basic Boat Navigation: How to Triangulate Your Position Video.
Create a Route with Bearings: Whether you’re planning a trip or you’re already on the water, you’ll need to know how to create a route. And unless you’re lucky enough to be going in a straight line with no obstructions in the way or channels to follow, that route will require multiple different bearings. Fortunately, this is an extremely easy process. Simply lay your parallel rules at your starting point, line the edge along the path you want to cruise, and draw a straight line on your chart. Then walk the rules until the edge intersects with the center of the compass rose, to get the bearing that corresponds with the line. Jot down the bearing next to the line, and you’ve created the first leg of your journey. Lay the parallel rules along the next leg, and repeat the process. And so on, until you create the final leg that intersects with your destination. When you cruise along each leg, you’ll know by glancing at the chart what bearing your compass should show.
Watch our Basic Boat Navigation: Creating a Route with Bearings to Navigate By Video.
Determine a Reciprocal Course: This is one of the simpler navigation tasks, but it’s also quite important. If you don’t know your reciprocal (reverse) course, you can’t go back the way you came. Since your compass has 360 degrees, the reciprocal of whatever course you’re on will always be 180 degrees away. If the initial course is less than 180 degrees, add 180 to get the reciprocal. If it’s more than 180 degrees, subtract 180 to get the reciprocal.
Ded Reckoning: This is a method of navigating from a known position to another position, using the information available to you, to deduce your approximate location. You need to know your speed, compass course, and the amount of time you travel, and record them all on your chart at every course change. If possible, you should include estimates of the effects of wind and current.
Here are the basic equations you’ll need to know:
- Speed x Time = Distance
- Distance / Speed = Time
- Distance / Time = Speed
WARNING: Never mix up MPH and nautical miles per hour, or knots. Mathematically you can use either when making these calculations—but not both. Since nautical charts measure distance in nautical miles (which equal 1.15 “statute,” or regular miles) it’s always best to stick with knots and nautical miles (NM) when navigating a boat with traditional means.
Let’s say your boat cruises at 20 knots, to keep the math simple. And let’s say you know you’re at position X at high noon, when a light fog rolls in. You can still see well enough to continue on your cruise at 20 knots, but visibility is limited to a couple of miles and your familiar landmarks are now out of sight. On your chart, you create a route home that calls for a five NM leg on a bearing of 200 degrees, and a second 10 NM leg on a bearing of 250 degrees. Divide five (distance) by 20 (speed) to get 0.25, which tells you that you’ll need to cruise for a quarter of an hour at 200 degrees. You use your watch or stopwatch to keep track of time, and at 12:15, stop the boat. Now record the time and your estimated position. Then turn to 250 degrees, draw your next course line, and again record your speed and bearing. Now you’ll need to divide 10 by 20, and you’ll know that you should reach your destination in half an hour.
Some people may find it easier to calculate how many minutes it takes to travel a nautical mile at your given speed and use that figure to navigate. That 20-knot cruise will take you one NM every three minutes, for example (60 divided by 20), so you can make the same calculations knowing that it will take you 15 minutes (three times five), or a quarter of an hour, to go five NM.
Ded reckoning can also be used to track your position as you travel an undetermined route in conditions of reduced visibility. Let’s say you’re heading on a compass course of 180 degrees when you leave the harbor. When your watch or stopwatch says 15 minutes have passed, you change course to 220 degrees. Record your bearing, speed, and time of course change. 15 minutes later, you can make a fairly good guess at your position—and keep track of your position as you cruise and make additional course or speed changes.
Ded reckoning is not, of course, an exact method. The ability of a helmsman to hold a steady course, wind and seas, and currents will all have an effect on how closely ded reckoning does or does not reflect your exact position at any given time. Cumulatively over long distances, little errors add up to become significant.
Watch our Basic Navigation: How to Navigate by Ded Reckoning video.
Once you have all these skills down-pat, you can get pretty much anywhere with your compass and basic navigational tools.
WARNING: all compasses are subject to magnetic interference, called “deviation”. Before any accurate navigation can take place, refer to the installation guide that came with your compass and “compensate” it (set it to account for deviation). If you don’t have an installation guide handy, Google can help.
Every mariner should understand basic traditional navigation, because you never know when your electronics will fail you. But truth be told, the vast majority of today’s boaters will almost always do their navigation on an LCD screen. The good news? Electronic navigation is far, far easier than using traditional methods. There’s bad news, too: those electronics can cost big bucks. When considering navigational marine electronics, you’ll need to choose among the following:
- AIS – Automatic Identification Systems are transmitters and/or receivers that identify most commercial ships and boats. They’re important for navigation because they can expose unseen dangers that lie along your course line, such as tugs and barges that are around the next bend of the river. Even if you don’t have an AIS system, when you’re within cell range you can access much of the information provided by AIS using an app like Shipfinder on your cell phone.
- Chartplotter – For the vast majority of us, this is the most important electronic nav unit. It provides you with a digital chart that can be used for everything from plotting a course to getting a fix on your current location.
- Fishfinder/depthsounder – Although depth soundings are on the digital charts used by chartplotters, they aren’t always accurate. Plus, depth can change with the tides or a lake or river’s changing water levels. So a depth sounder becomes invaluable when navigating through waters that may not provide sufficient draft for your boat.
- MFDs – Multifunction displays are informational hubs that sit at your helm, and can integrate all of the electronic units listed here onto one LCD screen.
- Radar – Radar broadcasts pulses which are reflected by solid items that may be beyond visual range, like distant ships or land. Essentially, radar gives you electronic eyes that can see for dozens of miles beyond the visible horizon.
Most boaters don't need all of these units. On most inland lakes, for example, radar and AIS aren’t exactly necessities. So, how will you know which unit(s) are appropriate for the type of boating you do? We thoroughly addressed this question, in Marine Electronics: What do You Really Need.
Let’s take a closer look at this little magical box of tricks in specific. It allows you to perform those key navigational tasks we identified earlier—locating your position, creating routes and bearings, and determining reciprocal courses. And it makes ded reckoning obsolete, since you always know where you are at a glance. Its digital maps, called “chartography” in nautical parlance, can be more or less detailed depending on quality and cost. Most are based on the data originally gathered by NOAA and/or by private services, and can be updated or geographically expanded either by adding a chart data card or by using a WiFi link. Many of the latest units can even be updated in real time using the data gathered by your depth sounder and GPS. To learn more about the latest in marine chartography, read Chart Transplant. And to see how a chartography update works, watch Boating Tips: Chartography and Software Updates for Chartplotters.
Locating your position on a chartplotter is as easy as looking for the boat icon on the LCD screen. It will be clearly visible on the digital map, with the exact latitude and longitude identified via the unit’s GPS receiver, and displayed somewhere on-screen. It’s as simple as that.
To create a route on a chartplotter, move the cursor to the position you want to go to, and press a button to create a waypoint. In the case of many touch-screen units, instead of pressing a button you’ll merely tap the screen. Press a “go to” button, and your bearing to that waypoint will be displayed. Turning the waypoint into a route is as easy as making more waypoints, or in some cases, pressing a “route” button so the unit automatically joins multiple waypoints together into a route. In most cases, your chartplotter will offer a steering screen that displays a digital compass or numerically displays your bearing, course, and other important information like time to destination, speed, and course error.
Determining a reciprocal course with a chartplotter is as simple as highlighting the waypoint you need to return to, and pressing that “go to” button once more.
It will, of course, take a bit of practice to learn which buttons to press when, and how your chartplotter model in specific works. But we can help shorten the learning curve—watch our How-To Special: Basic Chartplotter Navigation video to see how it’s done before you try using the chartplotter at your helm.
What about all those other electronic navigational aids? We’ve got you covered there, too. Check out these articles and videos, to learn the basics for each:
- AIS Basics: Automatic Identification Systems Explained
- How to Basics: Using Your Fishfinder
- Marine Electronics 101: How to Use Radar
Once you’ve got the basics under your belt, view these more advanced articles and videos which will help a navigational novice step up his or her game:
- Boating Tips: 3 Tips for Reading Radar
- Marine Electronics: The 10 Commandments
- Five Big Marine Electronics Myths
Is this a lot of information to absorb? You bet. Will getting used to both traditional and electronic navigation techniques require some practice and real-world experience? Absolutely. But armed with all of this knowledge, your basic navigational tools, and your electronics, you should have no problem navigating your boat from Point A to Point B—even in fog, rain, and darkness.