Accuracy wise I couldn’t fault the Garmin fēnix™ during the shorter runs I did, even when compared to two other Garmin GPS units. Heart rate, speed, distance, cadence and most importantly elevation data from the Barometric Altimeter were 99% the same and within a very small acceptable margin of each other. Satellite pickup was also quickly achieved as with the other Garmin units, avoiding the situation of standing at a trailhead and waiting for a GPS satellite fix before being able to start your trail run.
While the Garmin fēnix™ is an outdoors GPS watch, for the dedicated trail runner there will be times when they need to venture indoors to get the necessary training done. Luckily with the software updates the Garmin fēnix™ acquired the ability to connect to their footpod for indoor as well as outdoor training. Indoors the footpod will provide speed, distance and cadence information for those times when you have no option but to hit the treadmill. Outdoors the footpod will provide the Garmin fēnix™ with cadence information while also providing speed information (you have to specify if speed will be recorded via GPS or footpod), which is a great option in heavily forested or built-up areas where there may be a weak GPS signal. Take note that the Garmin fēnix™ won’t automatically switch from GPS to footpod if you enter a tunnel like other Garmin units. To record distance the Garmin fēnix™ uses the footpod while in indoor mode and the GPS receiver while in GPS mode, which is the standard configuration that can’t be changed.
In addition to the footpod, the Garmin fēnix™ also supports other ANT+ accessories, including heart rate belts, bike speed/cadence sensors (though it does not give speed data) and the Garmin Tempe external temperature sensor. While the Garmin fēnix™ does provide temperature data (one of my favourite features as I can see the effects of the weather on my performance as well as hydration/nutrition and clothing needs) it is slightly affected by body heat, so the Garmin Tempe is a great way to stay on top of what the weather is doing during a long ultra run for the reasons mentioned above, especially combined with the Barometer to see what the weather is up to.
Interface wise I found the buttons, large as they are, not ideally suited to quick presses during trail running. I had to press them quite hard at times or repeat a press that didn’t register, but I’m sure over the course of an ultra trail run where one slows down considerably that the larger buttons with their rough texture and long throw will become an asset as tired dess creeps in and one can take time to press the buttons properly. This should also prevent accidental presses over time. Initially one also had to do a long press on the up or down button (depending on your setup) to signify a lap completed, which meant an added second or two per lap time. Luckily as from the 2.70 software update one can now configure the bottom left ‘back’ button as a ‘hot key’, which means your laps will be registered immediately as you press the lap button.
I would have liked to see the screen be slightly larger, as I am used to my Garmin Edge 500 that can show eight fields of data per screen. I prefer a bigger screen with the data dividers as I find them easier to read at a glance while running. With the maximum of three fields displayed on the Garmin fēnix™ I struggled to make out the different data fields, so I found limiting the display to two data fields per screen (with the divider line in between) made for the best legibility. One can set up a host of screens (‘pages’) with 1,2 or 3 data fields per page. Another nice feature on the Garmin fēnix™ is the ability to display data fields on a page (only one per page) as a graph, which allows quick and easy tracking of, for example, heart rate data while trail running.