We live in an amazing time for navigation. Today, we can cross oceans using satellite technologies without knowing anything about celestial navigation or the intricacies of latitude and longitude. But there’s an obvious problem with this wonderful technology. What happens with it fails?
Boat compasses have been getting boats to their destinations for centuries. The compass is a key piece of navigational equipment that no boat should be without. Here’s a look at everything boat compass and a peek at a few of the best.
Navigation – A Reality Check
Besides being a basic navigation tool, the boat compass is a basic tool to help you steer the boat. When driving a car, you always have a visual reference of the road in front of you. Even if it’s foggy, you’ll have the highway stripes to keep you in your lane.
On the open water, however, there are no painted lines. In fact, every wave that hits your vessel tries to push it off course. On a sailboat, the pressure of the wind on the sails is always trying to pull you off-course and into the wind–a safety feature called weather helm.
When you’re pointed away from land, there’s nothing but a continuous blue horizon to guide you. Without visual references, it’s impossible to steer a straight line without something to guide you.
So, at the most fundamental level, a compass is as essential to a boat skipper as the road is to a driver. Without it, you would have no idea which way you’re pointing, nor would you be able to steer your boat in a precise location.
Types of Compass on a Boat
The fundamental tool of nautical navigation is the magnetic compass. It looks complex, but it is about as simple as it gets. Inside it is a magnet, and that magnet always points north. When you view the compass, you can read which way you are heading, using north as a reference.
Autopilot or Fluxgate Compass
Our modern technology also needs a heading reading so that a sail boat auto pilot can hold a course, or your chartplotter can plot your heading accurately. To do this, your boat will also have some type of electronic compass. The standard technology that makes this happen is the fluxgate compass. Just like a mag compass, the fluxgate uses earth’s magnetic field to point north. You’ll usually find this mounted in a cabinet in your boat. Make sure you don’t place anything magnetic in that cabinet because things can start getting out of wack.
GPS Compass – Course Over Ground
Finally, GPS receivers often plot a course on their screen for you. GPS devices only really know one thing–your position. But by tracking your position and how it changes over time, your GPS can interpolate a few key pieces of information. For example, it can determine how fast you are moving and in what direction. This looks a lot like a compass reading.
But, the GPS readings are slightly different than the heading indicated on your compass. The GPS is showing Course Over Ground. This would include any effects on the boat that result from currents or leeway from the wind. So while your mag compass indicates the direction the boat is pointed, the GPS shows your course as if it were plotted on the map. The two can be very different things in some instances. Additionally, GPSs might be set to point to true north, which is different than magnetic north!
Magnetic Boat Compasses
Here’s a little more detail about the magnetic compass, how to use it, and where you should mount one.
How Does it Work
The magnetic compass is a simple device with an internal magnet that aligns with the earth’s magnetic fields. It points north, and the lubber line on the compass shows your course. They reference the typical cardinal directions–north, south, east, and west. But it also breaks the compass into a 360-degree circle for more precise course plots. For example, north is 0/360º, east is 090º, south is 180º, and west is 270º.
Boat compasses usually have large cards that float in a fluid. This helps dampen the motion of the compass, making it easier to read when the boat is pitching and tossing. Most compasses also have an internal light, so you can use them at night.
Why Should You Have a Compass?
If you navigate on lakes, rivers, or near-shore waters, you might not use your compass very often. It’s probably something you take for granted.
The compass earns its keep when you head out of sight of land or when the visibility drops. In fog or at night, a compass is invaluable. If you have a good paper chart and a compass, a competent skipper should be able to find their way home from anywhere.
If you boat with a modern GPS chartplotter and an autopilot, you might not have looked at your compass for a long time. These items make navigating a boat so easy. But the danger in relying too heavily on these items is obvious. What happens when all these things fail one day? Not “if”–“when.” They will fail you. It’s a boat, after all.
Where Should a Boat Compass be Mounted?
It’s unusual for a boat to come without a compass. If the boat has a spot for the compass, it’s probably your best bet to mount it where the manufacturer intended. But if you’re designing your boat from scratch, it never had a compass, or you’re just redesigning the helm area, here are a few recommendations.
The compass is used much like the speedometer in a car. It needs to be right in front of your eyes so that you can glance at it and know what it says without thinking about it or trying. You don’t want to be turning your head or looking down. So you have to think about the helm for a boat, its layout, and exactly what spot would work best.
Most compasses are located along the boat’s centerline, but this isn’t always the case. They need to parallel the centerline. So if you have a sailboat with twin steering wheel helms or a powerboat with an off-center helm, you should ideally put the compass directly in front of the helm.
Location is just one consideration for compass location, however. Being made with delicate magnets, compasses are easily affected by other electronics on the boat. For example, place a cell phone next to a compass and see what happens–the compass swings wildly. So you’ll also want to plan your entire helm to put the compass somewhere isolated from other magnets, speakers, and electronics.
Styles of Compass Mount
The go-to company for boat compasses is Ritchie Navigation. Pretty much any boat you walk on–from kayak to luxury yacht–will have a Ritchie compass installed near the helm.
The company makes six styles of compass mounting hardware for each application.
- Binnacle–the typical steering column on a sailboat, with a binnacle-mount compass on top, right in front of the wheel
- Bulkhead–when the compass is mounted in a vertical panel, such as at the front of a sailboat cockpit
- Bracket–for mounting in any orientation–even overhead mounting, which is useful on small boats that don’t have a dedicated spot for the compass
- Dash–for smaller compasses, mounted into the dashboard on a power boat
- Deck/Surface–for mounting on a flat surface
- Flush–for mounting on a flat surface so that only the top of the compass shows
Hand Bearing Magnetic Compasses
You should also have a hand-bearing compass onboard. These compasses are handheld and can be pointed at objects to take compass readings or bearings. They are invaluable for collision avoidance as well as navigation.
Setting Up a Boat Compass
The compass is a self-contained item that has no connections to make. The only electrical wiring is the power connection to make the light run at night. But even without that, the compass will always work.
But that isn’t to say that you shouldn’t proceed with caution. You need to watch out for a few things when mounting a new compass. In addition to the things listed below, make sure you mount your compass precisely parallel with the boat’s centerline and on a flat and level surface so that the compass card swings freely.
Electronic Devices and Magnetic Objects
The biggest problem with compasses is that they can be interfered with. So, if you inadvertently mount your compass too close to your VHF radio or GPS device, it might indicate incorrectly. Even the smallest magnet can cause your compass to swing wildly.
Swinging a Compass for Magnetic North
Because boats are small and you can’t always eliminate electromagnetic interference, compass manufacturers build in compensating magnets. These magnets, usually mounted on the bottom of the compass, can be moved to counter the effects of other nearby devices.
Follow the compass maker’s instructions for adjusting the corrector magnets with the compensation screws. However, even once you’ve done the best you can, there will likely be a little bit of error in your compass. This is called compass deviation.
Take the boat out when you’re done and double-check your work with a marine chart. Make sure the compass readings are accurate and are not showing false reading on all headings. Make a deviation card so you know how much error there is on every different heading you might need to steer.
Best Boat Compasses
Here’s a handful of Ritchie brand compasses for boats. The choice comes down to which size and style fit your boat. Fancier compasses will have larger cards, easier-to-read numbers, and better dampening.
Hand-Bearing Compass – Nautos IRIS 50 Prism
A hand compass is a great backup to your boat’s compass, but it’s also super handy for taking bearings on various objects. This is necessary when plotting your position, standing anchor watch, or figuring out if another vessel is on a collision course with you.
Best for Kayaks and Small Boats – Kayaker by Ritchie with 2.75-Inch Card
This small, surface mount compass is perfect for small boats like dinghies or kayaks. However, this one cannot be compensated since it is designed for the smallest boats.
Small Dash-Mount Compass – RitchieSport X-21WW in White
This stylish two-inch compass will look perfect if your powerboat has a dash panel.
Bulkhead Mount Compass – Ritchie Navigation Venture SR-2-1
Many small sailboats and those with tillers have a bulkhead mount compass at the front of the cockpit. That way, it’s easy to see no matter where you are in the cockpit. This unit has both styles of compass cards built into one, which Ritchie calls the CombiDial. As a result, you can read your course directly on either the side facing you or off the top of the card.
Flush Mounting – Ritchie Helmsman with 3.75-Inch Card
This Helmsman compass will look sharp if you have a flat deck and don’t mind putting a big hole in it. It has a large card with the CombiDial design, built-in compensators, and directive force magnets.
Binnacle Mount – Ritchie Navigator Polished Stainless DNP-200
This is the classic binnacle mount compass found on sailboats everywhere. It features a 4.5-inch flat card, built-in compensators, and an internal gimbal system for stability in adverse conditions.
Don’t Get Lost Out There!
Compasses have become almost an afterthought in the day and age of GPS. But this simple item is critical equipment on your boat. So the next time fog rolls in and your GPS goes on the fritz, thank your compass for keeping you pointing in a straight line. Without it, you’d be doing circles out there for days!
Magnetic Boat Compass FAQs
Where do you mount a compass on a boat?
A boat’s compass should be mounted as close to the helm as possible. Generally, it’s right in the operator’s visual field, just like a car’s speedometer.
Where should you mount your compass?
A boat compass is mounted directly in front of the boat’s wheel.
Do you need a compass on a boat?
Yes! A compass is the only sure-fire way to steer a boat in a straight line through low visibility or when offshore with no other visual references.
How do you set up a compass on a boat?
Boat compasses need to be mounted correctly and adjusted before use. Any nearby magnets or electromagnetic fields can introduce errors into the compass. Follow the compass manufacturer’s installation instructions very carefully.