Technology on the Trail: Part 2: Apple Watch
Friday, November 11, 2016 11:30 am

My Apple Watch Sport was one of the few electronic devices I brought on my Appalachian Trail thru-hike. I brought it mostly for the novelty and for the (expected to be inaccurate) activity tracking, but it actually turned out to be far more useful than I anticipated.

Powering the Watch

The most frequently asked question I got on the trail was, “how do you charge it?” My answer was always some variant of, “Same way I charge my phone. I have a huge battery.” While in retrospect, it wasn’t a not a very surprising question (because the Apple Watch was unusual to see on the trail — I think I saw only one other, maybe), I still never would have thought so many people would ask me about charging my watch.

I had planned on running the watch in workout mode during the day, since I always used the Workouts app when out for day hikes or exercise, However, with “workouts” that were easily eight or ten, if not twelve or thirteen hours long, it turned out to not be feasible to have workouts constantly running. While I knew that workouts consumed power much faster than with it off, just how high the power draw was became clear on the first day of my hike.

When hiking the 8.8 mile approach trail from Amicalola Falls State Park to Springer Mountain, workout mode consumed so much power that as soon as I arrived at the Springer summit, I needed to spend a short while recharging my watch enough for it to make it to where I was making camp for the evening. After that, I didn't have the watch track workouts, which greatly reduced the its power budget.

What I also knew going in was that putting the watch into airplane mode (that is, shutting off its radios) would greatly reduce its power draw. I didn’t do this during the day so that it could stay updated with my phone, but at night, after the watch was fully charged and I was ready to go to sleep, I’d put it in airplane mode and use the excellent Sleep++ app to track my sleep.

In particular, I needed to be careful to not leave the watch plugged in for too long once it became fully charged. Once fully charged, the watch continued to draw power from the charger for as long as power was available, resulting in unnecessary drain on the battery. The iPhone, by contrast, stops charging itself once it’s fully charged, allowing the battery it’s plugged into to turn off.

With only two exceptions, the watch never lost power before I reached camp.

The first was one was due to a combination of thermal shutdown and excessive power use. One one particularly cold (below freezing) day in the Smokies, on the way to Clingman's Dome, the temperatures sapped the battery considerably. This was aided by my rain jacket, whose interior lining causes the watch’s display to think it’s been touched (causing it to turn on and try to do things, consuming unnecessary power in the process). After an hour or so of the cold and phantom touches, it shut off, and didn't turn on again until it got recharged in a warm hotel room.

The other time it lost power was towards the end of a particularly long, frustrating day going into New York, where I was out hiking for over 13 hours before stopping.

The only especially frustrating issue with the Apple Watch was that it required a relatively heavy device-specific connector to charge: the 0.3m charging cable was more than twice as heavy as the slightly-longer 0.5m iPhone cable I picked up to keep weight down.

I wound up buying and carrying a second watch charger the day after my two month anniversary on the trail. The short iPhone cable I bought developed a fray and needed to be replaced. It seemed prudent to pick up a second watch cable at the time, since that was going to be far more difficult to replace on a whim. Fortunately, I never needed it, but I would have been disappointed to have been in the middle of nowhere without a way to charge my watch.

Activity tracking was not so useful…

As I mentioned previously, I expected activity tracking on the Apple Watch to be fairly inaccurate. Specifically, I expected calorie counting to be low, as a result of the watch not understanding elevation change or that I was usually carrying a 30 - 45 pound pack. It didn't occur to me until quite a bit into my hike that my trekking poles were likely further confusing it.

Step counting (and by extension, calories burned) works by counting the number of times your arm swings back and forth, and combining that with measured heartrate. Usually, this is relatively well correlated with what your feet are doing. Not so when hiking with trekking poles.

Depending on terrain and inclination, when using trekking poles, your arms can swing anywhere between even with your stride (on steeper sections), or much slower than your stride (on easy, flat sections when you're not trying to use the poles for more speed). This can greatly throw off step counting and especially distance estimation. There was at least a few days where my watch claimed I moved ten miles further than I had actually gone, likely because it had gotten itself calibrated to two-steps-per-arm-swing on an easy section, and used that calculated very long stride length on a section with one-step-per-arm-swing.

With an active Bluetooth connection to my iPhone, the watch will attempt to use the phone’s GPS to recalibrate itself, matching your stride with how far GPS says you've moved. This failed, of course, the several times I turned off Bluetooth on either the watch or phone (or forgot to turn Bluetooth back on).

“Exercise” tracking was generally better: when I was in motion, the watch generally counted it as exercise. However, on particularly difficult sections of trail — usually with rock scrambles, or just really steep or hard to navigate sections — the watch would occasionally under-count exercise activity. It was surprising, to say the least, to spend an hour climbing up a mountain, only to find that I “only” exercised for half an hour.

Activity tracking, in theory, gets better results when explicitly using the Workouts app. Normally, the Apple Watch measures your heartrate every five or ten minutes (except when it detects consistent repetitive motion, because that somehow makes the sensor less accurate). This means that, in a hike, without using a workout, heartrate will likely only be measured when you're not moving (and thus, likely have a lower heartrate).

The Workouts app activates the heartrate monitor continuously, which could alleviate some of that inaccuracy. The downside to this, though, is that running the heartrate monitor continuously drains power at a much faster rate. (More on this later.)

… but watch complications were awesome

Measurement inaccuracies aside, I was still glad to have my watch. Though my phone was in an easily accessible hip pocket on my pack, my watch on my wrist was far easier to glance at, and it meant I didn't need to let go of one of my trekking poles to check the time. Being readily available allowed it to prove useful in ways I'd not even considered before my hike.

I used the “Modular” watch face, with five complications: date in the upper left; activity in the center; and weather (temperature), timer, and stopwatch along the bottom.

The weather complication was probably the least useful overall. While it was nice when it actually had data, when in an area with no cell reception, it displayed nothing of use. And, when you’re outside all day, putting a number to the current temperature doesn't actually help, especially without also knowing the humidity. If anything, it makes overly hot or cold days that much more miserable. “Oh. No wonder I feel so awful. It's 90°F out.”

The timer complication I used daily, to time cooking my dinner. Had I not had my watch, I could have used my phone, but having it on the watch was far more convenient. Also, quieter: the watch just vibrated on my wrist; my phone would have had to have made noise, since at dinner time, it was usually next to my sleeping bag recharging.

I quickly found the stopwatch complication to be useless, and changed it to the sunrise/sunset complication. This was useful many days, helping me to determining when I should plan to wake up, or providing a deadline for when I should arrive at camp.


The Apple Watch also allows you to sync a photo album from your phone, so that you can view the photos from the photos app on the watch. This came in handy a few times.

Although I carried a paper guidebook with me the entire trail, and kept it in a relatively easily accessible pocket in the “brain” of my pack, it was still a nuisance to pull it out to look at it. Thus, I began to take photos of the pages in the guidebook, using the photos app on my phone to look at them in a much more convenient manner.

However, on days with high humidity (or rain), it became very difficult or impossible to actually use my phone: eventually, the screen would become so saturated with water than it became unresponsive.

I found that the Apple Watch generally worked much better with water on its screen its screen than did my iPhone, so on days where I needed to look at the guidebook and it was too wet to use my phone, I was able to use my watch to view the pages.

Distance Estimation

As inaccurate as the activity tracking turned out to be, I was still able to use it to estimate distance traveled. On typical days, it wound up recording in the neighborhood of 75 - 100 kcal per mile, so I could use that as a vaguely accurate proxy for distance traveled, without having to pull my phone out and check the GPS track.

This was pretty handy, since I typically stopped for snack breaks roughly about every five miles or two and a half hours. Being able to easily check time or rough distance from my watch reduced the number and severity of interruptions caused by checking my phone to see how far I'd actually gone.


I was a little surprised at how resilient the watch was. A few times early on, the crown got a bit sticky and needed to be rinsed out with water, but otherwise, it worked perfectly well. Even getting drenched with sweat all day, every day, for six months didn't slow it down.

The few times I accidentally hit my watch into something, I think it managed to take more out of whatever it hit than developing nicks and scratches of its own.

Overall, I’m quite glad I brought my Apple Watch along with me on the trail, and it’ll be along with me the next time I’m out on an extended hike. It was entirely worth the weight in cables and battery to keep it charged. It substantially reduced the number of times I had to pull my phone out of its pocket, greatly lessening the number of times it could potentially be dropped, and it probably also saved me a substantial amount of power, since glancing at the watch uses far less power than turning my iPhone’s display on.

Technology on the Trail series

This post is part of my “Technology on the Trail” series:

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