What are .fit files for?

My understanding is that .gpx has a longer history as the traditional file sharing format among handheld GPS devices. It stands for GPs eXchange. Most websites only supported .gpx for file sharing. The .fit file format originated more recently with Garmin's fitness watches. With the 66i, Garmin decided to offer fitness apps along with traditional handheld GPS apps. More recently, many websites can handle .fit files as well as .gpx.

If you want to do fitness programs, there is no need to buy a fitness device, just use the 66i (though I'd rather have a wearable device than a handheld when doing fitness). This is where Garmin's Connect website and app come into play.

When it comes to recording a track, for hiking for example, I prefer .gpx. As I recall, the .fit file is automatically named with date and time when saved, and the name cannot be changed. I like to name my tracks with the trail name.  I record with .fit only and save to the Recorded Activities folder and then convert that file to a Saved Track.. I then go back and delete that particular recorded activity and rename the saved track. I do all of this on the device. I use Garmin's Explore website and app.

Alternatively, you could record with .fit and .gpx, but the .gpx file records into the Archived Tracks subdirectory within the Saved Tracks folder. When in the archive, the file isn't usable, it's just stored.  So you have to move it from the archive to the active Saved Tracks (called "Favorites") and rename it. And then delete the recorded .fit file.

In reality for myself, I record often while hiking to get real time data, but then I discard the recording when I'm through hiking. I only save a recording if I don't already have a .gpx file for the particular trail.  Typically, I'll find a .gpx file online prior to going onto a trail for the first time and download it onto the 66i.

Thanks, Like2Hike.  Good answer.  I doubt Garmin thought the 66i would be a fitness device when it was in concept with its long battery life, InReach capability, heft, etc.  Maybe the product developers forgot to tell the firmware writers that the 66i was a backcountry concept for people living, working and playing off the grid.  That might also explain the notion that web-based collections would be a useful alternative to Basecamp.

.fit is a Garmin-proprietary format. It is used for recording "activities". it is also used for "courses" in a routing context. 

.gpx is an industry-standard format for recording "tracks". Also used for "routes" in a routing context. 

Yes, nit-picking variations in terminology are confusing. But Garmin really, really wants all of their devices to be "unified" via common features - whether it makes sense or not.

.fit does a better job of accumulating totals, such as total distance. .fit accommodates various kinds of "fitness" data (for example, heart rate). Fitness data generally requires sensors of some sort in order to acquire the data. For wearables (for example, Garmin watches), some of these sensors are built-in. Some sensors are external and are connected via ANT+. For handhelds like the 66i, the sensors are always external and require ANT+ connection.

I would venture to say that most people do not use the 66i as a fitness device. So the ability to record activities in .fit format is a fairly useless "feature". .fit interoperability outside of the Garmin ecosystem is improving. But it still falls short of what is possible with .gpx. Proprietary binary formats such as .fit do not lend themselves to interoperability.

Personally, I configure my 66i to record in both .fit and .gpx format. Then I use the .gpx. it is a shame that you can't choose .gpx only.

Bottom line: If you don't use the 66i as a fitness device, and if you don't care about somewhat better accuracy of totals, .fit is indeed useless to you.

twolpert said:

Bottom line: If you don't use the 66i as a fitness device, and if you don't care about somewhat better accuracy of totals, .fit is indeed useless to you.

+1 

Thanks, twolpert.  I'm curious about what you said regarding totals.  Aren't totals straight addition?  How are the totals different for the two recorded formats?

I have no idea. That came from here: https://support.garmin.com/en-US/?faq=qn6PDmIjvs2TzPBDHULTD6

So it's either gospel or marketing smoke ;)

I'll keep thinking about that. But so far, I haven't even ben able to imagine how the total accuracy could be greater.  I assume both are just formats for storing the GPS track points and that totals are calculated by whatever program is reading the format.  Whoever wrote that web page should have realized that what it was saying required further explanation.  On the surface it sounds like  saying addition in Japanese is more accurate than in French.

I don't know why Garmin wrote what they did, but totals accumulate any errors via addition. So if you have a small individual measurement difference, between gpx and fit, that can be trivial. But if you add many small individual measurement differences to derive a total, the totals can differ more significantly, if there are many individual measurements.

Thaks, Like2Hike.  I don't see the relevance.  .fit and .gpx are formats for recording information. As far as I can tell, they are not ways of measuring positions or even distance between positions.  From what little I've read, the only difference is that .fit is a more compressed binary format of the same position information, and .fit provides for storing additional non-position datapoints like temperature or pulse rate that wouldn't have anything to do with distance between positions.