About Chartplotters

So, if GPS is just spitting out a series of numbers and the paper chart requires those numbers to tell you where you are, where does your chartplotter fit into everything?

The reason that I had you start thinking about paper charts first is because you can see the limitations of the chartplotter. Even if you project your electronic chart onto your 80″ screen, it is going to be a bit more difficult to see all the details that you can calmly peruse on your paper chart. That doesn’t mean that your chartplotter isn’t an amazing tool that we should all learn to revere and to harness.

Whether you are using small, handheld, the slightly larger screen of your smartphone or a state of the art 12″ screen, you have an amazing computer at your disposal. In most cases, the screen size just determines how much detail you can see at a time.

Modern chartplotters cannot only tell you where you are and help you determine the safest route to get where you want to be. That tiny computer tends to contain an entire library of pilot charts and tide tables, as well. You can find out the tide predictions for your favorite anchorage so that you know how much scope to put. Determine currents going through Ballast Point so you know whether to sail or motor. Most can even help you find a dock and dine restaurant. All of that before you even hook up the wind, depth and AIS instruments!

The best way to get to know your own chartplotter is to play with it. Zoom in and out to see how the level of detail changes. And you should be aware that even professional navigators have made the mistake of zooming too far out and not seeing details that could have saved their vessel (I’m looking at your, Team Vestas). Use it every time, even when you are cruising very familiar grounds, so that you are confident about what you are looking at should you go to less familiar waters. Set a course for your next day cruise and learn how to follow it – particularly challenging for sailors!

Don’t have a chartplotter on board? Download an app on your smartphone. At home, download OpenCPN and learn how chartplotters work, in general. How far out is 3 miles, where you can pump overboard? How far is it to Catalina? Where is the Mexican border on the water? What are those yellow buoys in the middle of nowhere? What would be your magnetic bearing if you were to follow the measured mile on Harbor Island? What is the best course to follow for a tour of Mission Bay? How long would it take you to run that course at 5mph (4.2kts)?
OpenCPN can also be used to do your preparatory chartwork. For most onboard chartplotters, naming waypoints and routes is a tedious process of scrolling through letters and symbols, so it can be nice to create a route on your computer and transfer the file to your chartplotter.
OpenCPN is opensource software. While it is free to download, if you find yourself liking it, you should consider a donation to the project. They have to pay for the servers to keep it available!

Keep safe, keep learning
Tanya Weimer