GPS, or Global Positioning Systems, are satellite-based navigation systems developed by the U.S. Department of Defense for military purposes&#;but they're familiar to most of us as the navigational system used by our phones and cars. Whether you&#;re talking about the GPS on your , in your car, or a marine GPS for boats, all these units receive radio signals from multiple orbiting satellites to determine your position.

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There are currently 30 active GPS satellites in orbit, plus some extras reserved as spares in case one or more satellites has mechanical difficulties or is damaged. By knowing the position of a minimum of three of these satellites, and calculating the time differences between the transmitted signals&#;which are moving through space at over 186,000 MPH&#;your GPS receiver can determine its exact position anywhere on earth. 

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How to Use Marine GPS for Boating 

The more satellite signals your GPS receives, the more accurately it can calculate that position, and while accuracy depends on a number of factors ranging from atmospheric conditions to receiver quality, when many multiple satellites are in view a common GPS receiver can typically put your position within a 16-foot radius. High-end receivers with dual channels can get significantly more accurate.

• Once underway, your GPS continually updates your position and provides speed and directional information.
• GPS also allows you to save positions, which we commonly call &#;waypoints.&#; For boaters, this can be helpful to permanently record the location of a channel, a shoal, or a fishing hot-spot.
• You can also string a number of waypoints together to create a route, taking you from point &#;A&#; to point &#;Z&#;.

Originally boating GPS units displayed your position in latitude and longitude, and while that information can still be displayed, on most modern marine GPS people use a digital chart to see where they are&#;much like you can look at a street map showing your position on your cell . A GPS that can display charts is called a &#;chartplotter&#; or &#;GPS/chartplotter.&#; And in recent years digital charts have become much more comprehensive in the areas they cover, have improved detail levels, and better accuracy. In fact, many modern chartplotters also allow you to improve the digital charts you look at in real-time as you operate your boat, by matching up your GPS position with depth soundings taken by your fishfinder.

Marine Navigation with GPS

Navigating with GPS is usually the most efficient, easiest way to navigate a boat, but far too many people use it as a graphical representation rather than a numeric one. You can display a digital chart on your GPS unit, and steer the boat in such a way that the boat icon at the center of the screen points in the correct general direction. But you&#;ll steer much more accurately if you instead use a dedicated &#;steering screen&#; that gives you the numeric compass heading you want to follow, the course you&#;re actually steering, and an arrow or indicator that tells you whether to steer to port or starboard to get back on the most direct course.

Be sure to read Marine Navigation: How to Navigate a Boat to get a more complete picture of navigating boats both with and without GPS. And remember: while most of us do depend on GPS to navigate our boats most of the time, no one should ever rely on it 100-percent. Like any electronic system GPS is subject to failure and you&#;ll need to know how to get back home when your electronics let you down.

Learn More: Marine Navigation: How to Navigate a Boat

Why You Need GPS on Your Boat

Even boaters who never leave sight of land should have a GPS/chartplotter aboard, on just about any boat. You never know when you&#;ll encounter fog, or a mechanical issue forces you to stay out late and navigate home in the darkness. And at times like those, you&#;ll be quite relieved you have GPS aboard. Plus, today&#;s units are so inexpensive (you can get a basic GPS/chartplotter for just a couple hundred dollars) that there&#;s really no excuse not to have one.

Wait a minute&#;your already has GPS, so why get another one just for your boat? That&#;s a good question, particularly because you can use a number of boating apps to more or less turn your into a mini-chartplotter. Cell phones, however, have a number of drawbacks:

• They aren&#;t always hearty enough to escape damage when spray starts flying or they fall off the dash and onto a fiberglass deck;
• They aren&#;t hard-mounted at the helm and few add-on mounts can take the vibration and impacts a running boat dishes out;
• Their batteries may run out faster than expected; and many boaters travel outside of cell coverage areas on a regular basis.

So while having a cell with a navigational app loaded up can come in handy and is a good back-up to have aboard, it should never be depended upon as your main navigational tool.

Other Uses for GPS on Boats

Anchor Alarm

A feature of GPS that&#;s useful to boaters in particular is the ability to set an &#;anchor alarm.&#; You can establish a geofence around your boat while it&#;s at anchor, and if the anchor drags or the line comes loose and your boat goes through the geofence, your GPS will sound an alarm.

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Security System

Some of today&#;s systems also allow you to interface with your boat&#;s GPS from afar, via an app on your cell , so it acts as a security system. You can set that geofence up around your boat, and if someone tries to steal it, you&#;ll get a text alarm as soon as it moves out of position.

Additional Features

If your GPS is &#;networked&#; (wired to the other electronics aboard the boat) it can also fulfill a number of additional functions.

• It can let the autopilot know where to steer, overlay additional data (like boat radar) over the digital charts.
• Perhaps most importantly, give your VHF radio the boat&#;s position data. When your VHF receives position data you can use it for DSC (digital selective calling). Do so, and if you ever have to call the Coast Guard they will receive your exact position data via the radio transmission. This is a potentially life-saving feature, so be sure to take a closer look at VHF communications and DSC by reading How to Use a VHF Radio.

To learn more about GPS and see the government&#;s official statements about it, read FAQs, and more, visit the official U.S. Government GPS website.

Read Next: 5 Best Marine Navigation Apps for Boaters

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What Does Your Boat Need?

So you bought a boat. Now what?

Life on the water is great, but it can come with a lot of questions. You probably need some technology or additional equipment, but how do you know what to look for? Do you need sonar? Which chartplotter is right for you? What is a chartplotter?

No worries. We&#;ve got you covered. We make some of the best technology for all types of boaters, and we&#;ve made it easy for you to find out what you need. Start by scrolling down to learn a little bit more about marine technology, and why you might want to use it on your boat. We&#;ve made a list of everything you might need, organized by how they help you make the most of your time on the water.

For Navigating

Whether you have a coastal power boat, a fishing boat you use on local lakes or a sailboat, we&#;ve got all the navigation equipment to help you plot the course for your next adventure.

• GPSMAP® x3 chartplotters: While we know the first thing you probably think of is navigation, Garmin chartplotters can do a whole lot more than get you where you&#;re going (thought they certainly do that). Consider a chartplotter the brains of the operation. They can be used to show data from other equipment on board like radar, engines, lights and more &#; even to see what&#;s under the water around you when paired with a transducer (sold separately). Using GPS, chartplotters can show your exact location on a navigational chart, along with heading, speed and other information.
• ActiveCaptain® app: Downloaded on your compatible smartphone or tablet, this free, all-in-one app creates a powerful connection between you and your Garmin chartplotters, charts and the Garmin boating community.
• Garmin Marine charts: We don&#;t need to tell you the importance of these. Even Magellan had charts. Of course, his didn&#;t include features like high-resolution relief shading or satellite photography.

For Fishing

Do you get out on the water for the fish? If you&#;re looking for the catch of a lifetime, then these products are built for you. The sonar capabilities in Garmin fishfinders make fishing so easy, it almost feels like cheating. 

• Transducers: With the capability to pair with Garmin chartplotters and/or fishfinders to provide a crystal clear, easy-to-use interface, Garmin transducers provide sonar readings of the water underneath the boat so you can see bottom structure, fish swimming (or hiding from you) and more. The Panoptix LiveScope&#; System pairs with compatible chartplotters and is the top of the line, with stunning, real-time imagery below and around your boat up to 200&#;. The GT56 pairs with compatible chartplotters and fishfinders and is a versatile, all-in-one transducer featuring ClearVü, SideVü and traditional sonar.

• ECHOMAP&#; Bundles: Pair these chartplotters with our transducers to get the best in sonar and built-in cartography for navigation. If you&#;re serious about fishing, you&#;re going to want one of these. 

• STRIKER&#; Vivid Series help you find the fish from your boat. Through built-in sonar, you can see fish and underwater structure in crisp detail. You can mark any good fishing spots &#; and even choose different color options.

• STRIKER&#; Cast: Just attach this handy sonar device to your fishing line and cast. Reel it back in to view sonar with a 200&#; castable range via an app display on your compatible smartphone or tablet. In addition to heading out on your boat, this product is a great fit for you if you own a kayak or sometimes fish from shore.

For Entertaining

What is the point of a party on the water if you can&#;t crank the tunes? Whether you&#;re into flashy, heavy bass or something a little more subtle, we have a full suite of marine entertainment products to help you customize a sound system for your boat.

• Fusion® MS-RA60: This is our durable, economic marine stereo. It&#;s modern yet retrofittable, and you can control the music from your compatible smart device or Garmin watch.
• Fusion® Apollo® Series: If you want a marine stereo with the best in audio quality and innovation, you&#;ll want one of these. Custom audio profiles, seamless high-quality streaming and an option for a touchscreen console.
• Fusion® Signature Series 3 Marine Speakers: These speakers don&#;t just feature an option for multicolor LED lighting but also superior sound quality and a 3-year warranty.

For Sailing

If your picture-perfect day on the water includes a sailboat, you might need help to harness the wind &#; literally. We have some great instruments (code for screens that will show you all the wind, wind angle and depth data you could want) and sensors to help you capture that data.

• GMI&#; 20: Sporting a bright 4&#; color class-bonded lens display with anti-glare finish, this is more than just a wind instrument &#; it also shows speed, depth and 100+ marine and vessel parameters. If you&#;re into racing, it&#;s also got a dedicated race timer that counts both down and up.
• GNX&#; Wired Sail Pack 52: If you&#;re looking to knock out all of your sailing needs at once, this bundle has everything you need to know exactly what&#;s going on with the wind and water around you.  

For Staying Safe

Ideally, this is a priority for everyone on the water, regardless of whether you&#;re into speed racing, partying on pontoons or somewhere in between.

Are you interested in learning more about marine navigation equipment? Contact us today to secure an expert consultation!

• Fantom Radars: It&#;s pretty important that you be able to see what&#;s coming. This suite of radar technology highlights moving targets in color and fully integrates with Garmin chartplotters to show you what&#;s headed toward you &#; or away from you. On the water, it&#;s best to keep surprises to a minimum.
• VHF 215 AIS Marine Radio: With a built-in GPS, distress calling, direct calling and frequency bands that include all U.S., Canadian and international marine channels, this marine radio increases peace of mind and will allow you to communicate with confidence on the water.
• MSC&#; 10 Marine Satellite Compass. This compass does a whole lot more than just pointing due north. An easy-to-install, multi-band GNSS receiver, you&#;ll get detailed tracking that even includes pitch, roll and heave information if the water is feeling a little choppy.