Apple Health App vs. Garmin GPS. Distance on foot.

Woods Walker

The Wood is cut, The Bacon is cooked, Now it’s tim
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Disclaimer for those loving internet drama. Electronic tools do not replace navigation skills and tools such as map and compass, looking around etc etc etc. These are just more tools for the box.


Often I like to measure distance traveled on foot. This is a good way to know if trip goals are being met. Also great for training and a good tool for navigation. After all if a destination is 10 miles away and you already walked 20 odds are something is wrong. I compared both devises to measure distance. Speaking for myslef I have noticed accurate measure of distance on foot can be challenging given all the variables. For example this sign stated 14 miles to my destination. In the end I needed to go to South Wilcox which is an additional 2 miles. No water at the first location. I walked .5 miles to get to this sign for the shelter yet after all was done and said my IOS showed 22 miles. Somehow I gained an additional 5.5 miles. I have also noticed sometimes the GPS seemed short compared to the map. Both issues appeared more prevalent in hilly country but that's just my unscientific observation so could be wrong.





I decided to run two tests. One was less formal however at night so more fun. The other was more precise which is on video. Really I was just looking for a reason to cover some ground so used this as a pretext to get away. Both tests were on a popular trail. There are actually multiple trails so picked the flattest one with the least amount of obstructions. So lets do the night one first cuz we got a night trout. That's right an actual night trout. Frogs as well!


The night trail running gear.





Using lithium ion for both the MD2 and Nitecore HC30. Lots of power!





The Garmin GPS. I will be using my iphone SE for the IOS health App.





As I was going over my gear this frog showed up. Fantastic!





I set the tracks to record the outing. Garmin GPS.





The river was low.





If you look hard in the middle of the hot spot there is the promised "night trout".





Rocks are cool.








Not sure I like spiders.





Tracks all done. Basically trail jogged from a parking lot into a town park then back. Garmin GPS.





What's the distance. Garmin GPS.





What's on the IOS Health App.





I remembered having around 6 miles already as this was done during the last few hours of the day. So decided a more exact test would be called for however the numbers appeared very near.


Test 2.


A day slow jog on the first part of that same trail but on the widest flattest part with an exact predetermined distance. The map said 5.25 miles. To keep the test true I wouldn't stop for photos etc. Just keep on moving till the end. Also carried an action cam in my right hand for the entire run. That was a bit of an inconvenience as needed to keep that arm still. The run and other information for the second test are on the video.


Map.


States 5.25 miles.


Garmin GPS results. Trip computer.





Time. Garmin has 1 hour 6 minutes of moving time. The IOS has 1 hour and 9 minutes. This spot on as started to measure the time before putting the device inside my pack etc.


Distance. The Garmin measured 5.25 miles. Top speed of 6.1 mpr, Average speed of 4.7 mpr and overall speed of 4.1 mpr. The IOS device measured 5.63 miles. The IOS had .02 and Garmin .01 already registered before the test via walking to the truck etc etc. Per my calculations the average speed should be 5.01 mpr. Not the world's fastest run but that wasn't the goal. The GPS seemed within the ball park. The saved track showed 5.41 miles but took the trip odometer photo immediately. The track wasn't saved till about done packing up so might have slightly corrupted the saved track results however trip odometer is spot on. Not sure why the extra distance as don't remember moving around great deal between the odometer photo and final savings. Still it is what it is.





Apple IOS Health App. To ensure I wouldn't have too much clutter from daily activity used an ipod touch rather than iphone.


Time.





It is an electronic timer so no questioning the accuracy however it wasn't all actually moving time. I had to put the device into a dry bag as thunderstorms were predicted and lock up the truck before heading out. Then needed to unpack it to stop the timer. Still there wasn't much difference between the two.


Distance.





5.63 miles is longer than both the map and GPS however not by much. I hardly jogged in a straight line and unless mistaken this is based on actual motion. Then again there was a bit more initial distance on the ipod than GPS before the outing. Say .02. We are taking about a very small difference no matter how it's interpreted.


Conclusion.


Within the context of this controlled test both Apple IOS Health App and Garmin GPS were accurate enough. It's very possible hills or mountains could influence the results but this test was done over a mostly flat dirt road trail. I believe the IOS devise measures motion and Garmin GPS distance but not necessarily taking all steps and motions into account. During past tests I have noticed greater distances recorded on the IOS than the map or GPS showed however up and down hills, stepping over and around rocks etc etc might influence the Apple motion coprocessors which isn't a bad thing as I don't travel on foot as the crow flies. This is all speculation on my part as not a technical person.


Video of second test.





Thanks for looking!
 

StarHalo

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Great comparo. Interesting that the iPod gave you the longer distance; I've walked many days 12-15 miles at work with both my iPhone and Fitbit, and the phone consistently reads less distance than the pedometer.
 

Woods Walker

The Wood is cut, The Bacon is cooked, Now it’s tim
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Great comparo. Interesting that the iPod gave you the longer distance; I've walked many days 12-15 miles at work with both my iPhone and Fitbit, and the phone consistently reads less distance than the pedometer.

Others complained the fitbit wouldn't read correctly when they were shopping as their hand was stable on the cart so it gave less distance. I bet types of activity determines how these motion things calculate distance. Who knows? What is that saying? If you take the state of New Hampshire and flatten it out the area would be the size of Texas? Or something like that. Not even sure that saying is true. :shrug: Distance on foot is hard to determine IMHO or at least for me. Keep up the walking. It's good for yea!
 
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mattheww50

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Both of these devices depend upon GPS, and I'll give you big odds on the Garmin being more accurate. The problem is that the CEP on the Garmin (if it us able to utilize WAAS augmentation) is on the order of 3 meters. That means that there is an error in each position, and distance between each position of up to 6 meters. Over a long period one can expect these errors to largely wash out. It is unlikely the IOS device supports WAAS augmentation, which makes the CEP on the order of 10 meters at best making the potential error between two points up to 20 meters. Once again with enough time, these errors should largely washout. However you are dealing with a much larger error to begin with, so it will take much much longer to wash out. The IOS device is not a dedicated GPS. It is kind of like the difference between the camera on an Iphone versus a dedicated digital camera with a significantly larger image sensor. The dedicated camera is likely to be considerably more capable because that is what it is designed to do. Both the camera and the GPS on the IOS device are designed to live within the time, processing and power constraints imposed by IOS hardware. I.E. they involve compromises that a dedicated device does not have. The Garmin GPS is a GPS, and while there are some constraints on power consumption because it is battery powered, there are none on its time or processing requirements (and WAAS requires considerable processing).

The other question I would ask is what the update interval is on the IOS GPS function. I suspect it is longer than it is on the Garmin, and the GPS in both cases calculates distance as the straight line distance between the fixes. If there is more than one step between each fix, then it is calculating the straight line distance between the fixes rather than the actual distance you may walked. In terrain, you probably cannot go very far in a straight line. Again, running the GPS takes power, and reducing the update interval decreases that. The update interval on the Garmin is probably on the order of 1 second. the longer the update interval, the larger the resultant difference between actual distance walked and that reported by the device.
 
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Woods Walker

The Wood is cut, The Bacon is cooked, Now it’s tim
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New England woods.
Brother you know more than me. I just took them both running for 5ish miles and read what they said. Can't really answer most of your questions. That said it was a very informative response! Great info.
 
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