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  1. #1
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    Droid vs iPhone vs garmin on Strava

    Over on the x/c forum there is a discussion about the gps tracking that these platforms perform for Strava. Anyone here do a head up test of how different the Droid, and IPhone app, or a Garmin unit record data for Strava? Looking at sensitivity issues and recording route points between the various units.
    I wondered if anyone had tested the 3 units head to head to see the differences.


    Strava update, now with more Suffering!

  2. #2
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    I haven't tested them but I have been in groups where people have garmins, iphones, droids all on the same ride. I find them all to record data somewhat accurately, but we all ended up with different times and elevation changes. Also, this was on the road, I'd imagine the differences would be greater offroad.

    Still, the differences weren't that great that I would discredit any of them. I have a garmin mostly just because its smaller than the other two if you want to mount it to the bars and the battery lasts longer.
    Hey guys, lets go play bieks!

  3. #3
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    Phones are a mixed bag. A huge mixed bag. Some of them are absolute ****, and others aren't bad. The problem is, that without buying and tearing apart every model of phone out there, we won't ever know all of the details that affect GPS accuracy. I think when it comes to the GPS processor chipset, most phones are using similar ones (and they are different from the chips that standalone receivers use). I think the biggest difference comes from the antenna used in phones. I'm pretty certain most use pretty small ones. Comparing the phone to a Garmin in a populated area with good cell reception doesn't give you the whole story, because phones are using the cell antenna to augment the GPS signal and improve accuracy and acquisition speed. To get a real apples-to-apples comparison, you need to be in a place with zero cell signal so the phones can't augment. And this is where differences start to shine.

    There is also the variable you can add of buying an external GPS receiver for your phone. Most are wireless (bluetooth) these days, but they've been around for a long time now. They basically give you the same kind of GPS reception you get on your Garmin and bypass the phone's GPS hardware. Couple folks here have gone that route and have noticed significant improvements in data quality on their phones.

    The limitations of a phone's GPS hardware also won't crop up much on a road ride. MTB rides are much more difficult to record accurately. Elevation especially is notoriously difficult to measure. Since the phone does not have a barometric altimeter, it is receiving elevations from a database that whatever app is using based on its GPS position, or, the phone is calculating those elevations based on the GPS signal which is less accurate for consumer equipment (it will likely be impossible to tell which method a particular app uses). So obviously those elevations will depend on the GPS accuracy. When you have a barometric altimeter recording elevation, it is doing so independently of the GPS. It has its own accuracy issues mostly related to changing barometric pressure over time. Calibration is important. Newer Edges have an auto calibration feature. Handheld models require a manual calibration. Old Edges didn't have any kind of calibration for awhile.

  4. #4
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    Quote Originally Posted by NateHawk View Post
    ....
    Elevation especially is notoriously difficult to measure. Since the phone does not have a barometric altimeter, it is receiving elevations from a database that whatever app is using based on its GPS position, or, the phone is calculating those elevations based on the GPS signal which is less accurate for consumer equipment
    ...
    Lots of phones (androids at least) have barometric altimeters. Many Sonys for example, and the very common Samsung S4. (EDIT after checking Strava site: It seems that the Strava android app doesn't currently use altimeter data! My bad for not noticing this. Many other GPS recording apps do.)

    Many phones also support GLONASS (iphone 5, most current Samsungs, HTC, Sonys..), which means satellite availability is potentially much better in some conditions. Almost none of the Garmin sport models support GLONASS.

    I don't claim to know whether these pros/cons make a significant difference in real-world accuracy. We'd need actual data, rather than conjecture, to test that.

    Dcrainmaker did some comparisons a while ago.

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    I have done some reading about GLONASS. The addition of GLONASS satellites doesn't always improve accuracy. The GLONASS network is a little bit less accurate than the US GPS system on its own. GLONASS adds benefit by providing more satellites in situations with difficult reception and on its own provides better accuracy farther north (it is designed to work better at far northern latitudes). This is most important for phones, which have poorer reception in general, so they will see the most benefit. I have a suspicion that this is why Garmin has had a less than overwhelming endorsement of chipsets that offer GLONASS capability (the Edge 510 does but strangely the Edge 810 released at the same time does not). GPS+GLONASS chipsets are taking off in handhelds, though, with many offering them. It is also worth noting that GLONASS speeds acquisition times, and the first source I cite notes that GLONASS chipsets take up more space. Not sure if that has anything to do with the Edge 810 not getting one.

    http://deltas.blog.com/2012/12/05/gp...-vs-glonass-2/

    Consumer GPS/GLONASS: Accuracy and Availability Trials of a One-Chip Receiver in Obstructed Environments : GPS World

    I think multiple GNSS chips will really take off when Galileo hits full coverage and there will be 3 global constellations to choose from.

  6. #6
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    Quote Originally Posted by SpeshulEd View Post
    I haven't tested them but I have been in groups where people have garmins, iphones, droids all on the same ride. I find them all to record data somewhat accurately, but we all ended up with different times and elevation changes. Also, this was on the road, I'd imagine the differences would be greater offroad.

    Still, the differences weren't that great that I would discredit any of them. I have a garmin mostly just because its smaller than the other two if you want to mount it to the bars and the battery lasts longer.
    I too ride frequently with others who track rides using Garmin's (200, 800 and 810; no Droids). One occasional rider has an old school cyclecomputer with an accurately calibrated wheel sensor.

    I've used Cyclemeter on various iPhones over the years and find that distance stats deviate by a max of ~8-10% when I compare to the others which is fine by me. My Garmin tracking cohorts are of the opinion that their devices do not account for stopped time correctly (which might explain some ride time disparity).

    Elevation numbers on models of iPhone up to 5 are also off (similar to Garmin 200) which does not bother me either. For example, on a recent ride Garmin 800 reported 7,400 ft of elevation and a Garmin 200 came in at 5,740 ft. I haven't compared the accuracy of the iPhone 5s barometric altimeter against an 800 or 810 yet...

  7. #7
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    Quote Originally Posted by edubfromktown View Post
    I too ride frequently with others who track rides using Garmin's (200, 800 and 810; no Droids). One occasional rider has an old school cyclecomputer with an accurately calibrated wheel sensor.

    I've used Cyclemeter on various iPhones over the years and find that distance stats deviate by a max of ~8-10% when I compare to the others which is fine by me. My Garmin tracking cohorts are of the opinion that their devices do not account for stopped time correctly (which might explain some ride time disparity).

    Elevation numbers on models of iPhone up to 5 are also off (similar to Garmin 200) which does not bother me either. For example, on a recent ride Garmin 800 reported 7,400 ft of elevation and a Garmin 200 came in at 5,740 ft. I haven't compared the accuracy of the iPhone 5s barometric altimeter against an 800 or 810 yet...
    I don't think anyone does a really good job measuring stopped time in the field. I prefer to get those metrics after I download my track to my computer when I get home. I think Topofusion does a pretty good job of breaking down metrics for each individual ride.

  8. #8
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    Quote Originally Posted by edubfromktown View Post
    For example, on a recent ride Garmin 800 reported 7,400 ft of elevation and a Garmin 200 came in at 5,740 ft. I haven't compared the accuracy of the iPhone 5s barometric altimeter against an 800 or 810 yet...
    My 810 likes to give me extra elevation ft too. I don't mind so much though because it makes me look more badass. ha!
    Hey guys, lets go play bieks!

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