What can you do with your GPX data? What is GPX data? Why should you care? If you’re on a sailboat with a chart plotter or multi-function device (MFD) and GPS, you probably generate GPX data whenever you move the boat. GPX data is nothing more than a collection of GPS waypoints that, when strung together, form a track.
Tracks are one of the most useful tools we have onboard. It allows us to precisely record where we have been, just like the brother and sister in the 1812 Brothers Grimm fairy tale with their breadcrumbs. Why is that useful? Because we know that – if we stay on the track and provided conditions are relatively the same as when the track was recorded – we will be safe.
Having a track is what allows us to enter an anchorage during the daylight hours, spend the night, and leave before sunup, safe in the knowledge that we probably won’t hit anything on the way out as long as we follow our track.
Of course, there are limitations. Tides can play havoc with tracks. As can other vessels. But in general, a track is a useful tool when navigating in less than ideal conditions.
Tracks can also be shared. If you have a friend with a boat that draws 7 feet, and yours is the same or less, their tracks can be a useful tool. And if you trust your friend’s judgement, you can still use the track even if your draw more than they do.
DOUBLESTAR draws just about 8 feet, and we never thought we would be able to get close to the infamous “drug smugglers’ wreck” off Norman Cay in the Bahamas. But friends of ours on a beautifully restored 47’ Kaufman had visited this anchorage.
While they draw less than us, they confirmed we could get in provided we followed their track. We did, it worked out great, and we had an amazing time. Thanks guys!
Track data is also what services like PredictWind use when they provide tracking information for vessels. You have probably seen your friends, fellow sailors or your favorite sailing YouTubers with a page that shows their current position, for example the Ryan and Shopie Sailing live tracker.
While we are PredictWind users, we do not use their live tracking service. For one, we do not have an Iridium GO on board, which is needed to record and upload the tracking data. It’s also used for downloading the PredictWind forecast, we have our KVH satellite for that purpose.
More importantly, we are not super keen to have our position broadcast in real time. Call us old school, neurotic, paranoid or just stuck in generation where putting EVERYTHING out there is just not done.
The point is, we often update our publicly available position only after we have left a location. As and when we can, or feel like it. But to do this, you need a few more steps (compared to the Iridium GO/PredictWind setup that just does it automatically and carries a subscription cost for the convenience).
Having your track data exported and visually presented (other than on your chart plotter or MFD) is also a great option to ensure you have a log of your travels. If the boat ever sells, or your chart plotter/MFD gives up the ghost, you have a backup and a visual reminder of your travels for posterity.
To create a visual representation of your track (other than on your chart plotter) you need 3 things:
- Map software
- GPS data
- A way to get the waypoints to display on the map software
What would be really nice is if there was a way to combine all of the above for free.
The good news: there is!
- Map Software
If you’ve used any kind of navigational aid (whether in your car, or on your boat, or during a hike) you have used map software. Google Maps, Google Earth, Bing Maps, Apple Maps … these are all examples of widely used consumer mapping software.
The companies behind these make their map data and servers available to developers who want to provide additional services or functionality, with the map as the underlying source data.
For example, if you plan a road trip and use an app to see what attractions are available along the way, the app developer has likely licensed an API (application programming interface) from Google or one of the others to provide the mapping data, and then built the places-of-interest data on top of that.
One of the most popular third-party applications that have been built in this way is WP Google Maps. As the name implies, it is a Google Maps plugin for WordPress. WordPress – if you happen to live under a rock or still have a Nokia cellphone – is the world’s most popular website creation software (technically, a Content Management System or CMS).
4 out of 10 websites are created in WordPress, including the one you are using right now.
The WP Google Maps plugin allows you to create tracks by importing GPX data. And it’s free. (There is a premium version available for a one-off fee of $40 which adds some cool additional features). We have no affiliation with WP Google Maps.
Download it here:
- GPS Data
The tracks you generate while sailing (regardless of whether you use B&G, Raymarine or others) is a collection of GPS data. This data is stored on your chart plotter/MFD and can be exported. I am not sure how this works in brands other than B&G, but I am confident pretty much every chart plotter released in the last 10 years has this feature. Let me know if I am wrong.
Google how to do it on your particular model. Here I will cover data export on the B&G Zues3.
First, make sure you are actually tracking your route. The Zeus3 is good for about 23,900 GPS points per track. By default it tracks at a very high frequency (I forget what it is exactly) but you can change these settings to ensure your tracks are longer.
From the B&G main menu, tap on Waypoints, Tracks then Settings:
I set mine to record a new GPS position every 0.05 nautical miles. With 23,900 recorded points per track, a track is good for about 1,200 nautical miles, which covers most passages.
On longer passages, such as the one we just did from Panama to Cancun, I would start a new track halfway through the passage to ensure I cover the entire distance. Or I could change the settings to log every 0.09 miles, which would extend the track range to over 2,100 nautical miles, but the track resolution would be less accurate.
Now, while WP Google Maps can certainly read GPX data, it cannot read the B&G export data natively. WP Google Maps is looking for a GPX file in a very specific format before it will be able to process the data points.
After much fiddling in Excel with trying to remove unwanted data points (and if you know Excel, you know it’s not super-efficient at working with 24,000 data entries!), I decided to dust off my old software developer synapses (which had been collecting dust in my cerebral self-storage unit with the rent barely paid up) and wrote a quick Windows application to allow me to convert any exported B&G track to a file that is friendly to WP Google Maps.
Why a Windows application and not a fancy online app? First, I was just doing it for myself.
Second, when I realized it may be useful to others, I was too lazy to go through the process of registering (again) as an app developer and get permission to make an app available for download on Google Play and Apple App Store.
Third, I did not think enough people would be in the unique position of needing this type of program. I still don’t. I am posting this to help maybe that one other guy or gal that has the same problem I had.
And finally, security and permissions. When developing software for online distribution security and user permission management become major issues. By keeping this simple as a good old fashioned Windows application that you actually have to install, it makes my life simple.
Heck, you could even distribute this via … gulp … CD-ROM!
So head onto our downloads page to grab the little program, install it, and then check back here for how to use it.
We first need to export the source file from the B&G (or whatever make you use) device. On the B&G Zeus3, follow this sequence:
Once the export process is complete (depending on the amount of data, it could take some time) you can copy the data from the removable media to your PC or laptop.
To convert the GPX data that you just exported to a format that is readable by WP Google Maps, launch my little Track Generator app that you downloaded. Follow this sequence:
Now all that remains is to import the converted file into WP Google Maps. Open your WordPress admin or whichever application you are using to access WP Google Maps settings, and follow this sequence:
And that’s it. We’ve successfully exported (and backed up, don’t forget!) our GPX data from our chart plotter or MFD, and massaged it into data that our free WP Google Maps can use. We can now display this, share it and add to it.
Is it more laborious than just going with the PredictWind/Iridium GO solution? Absolutely! But not only is it free, you also have a lot more control over what your display, when you display it and how it is displayed.
And I like options!
Contact me if you have any questions or suggestions on this page, the application or anything else.