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10496 Views 16 Replies Latest reply: Oct 28, 2011 10:51 AM by rjsams 1 2 Previous Next
NolanShanahan Rookie 3 posts since
Sep 5, 2009
Currently Being Moderated

Jun 13, 2011 1:50 PM

Accuracy of GPS Watches vs. iPhone GPS

As one of the many runners who is also a tech geek, I am extremely interested in tracking my mileage, routes, pace, etc. when I run.  I currently use my iPhone and have tried several different apps - iMapMyRun, RunKeeper and Nike+ GPS.  Each has their own pros and cons but my biggest issue with all of them is the general inaccuracy in terms of route and distance.  I live in a suburban/rural area and run exclusively on the roads but when I finish and look at the map of my route, it has me cutting across backyards, etc.  On a 5 mile run, the routes are sometimes off by .5 or more which in turn makes the pacing information less than accurate as well.  I'm willing to spend the extra money for a watch with GPS but don't want to do so if I'm not going to get increased accuracy.  Are GPS watches generally more accurate in terms of distance/route calculation than the iPhone?  I'll admit that I don't know much about the technology behind GPS - does the fact that I live in the mountains and run on roads with a good amount of tree cover mean that any GPS unit will have issues?


  • Katie21784 Pro 128 posts since
    Apr 5, 2011
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    1. Jun 13, 2011 2:13 PM (in response to NolanShanahan)
    Re: Accuracy of GPS Watches vs. iPhone GPS

    I'm not much help on this, but I'm interested to see the response you get.  I've also noticed that my routes in my phone (Droid - Galaxy S to be specific) seem to be inaccurate using iMapMyRun.  I haven't had MAJOR differences, but even a slight difference screws up the calculated pace like you said.


    I'll also throw out...for the women runners who use a GPS watch is it too big and bulky?  I'm a very small framed girl so the size of a GPS watch is also one of the things I've worried about when it comes to investing the money into one!

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  • protometal Pro 124 posts since
    Aug 31, 2010
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    2. Jun 13, 2011 2:46 PM (in response to Katie21784)
    Re: Accuracy of GPS Watches vs. iPhone GPS

    I have a Garmin 205 GPS watch and love it. My experience is that it is extremely accurate and I have not had any signal issues on moderately wooded neighborhood streets. (I have not taken it into a full-on forest.)

    I connect it to my computer and save info on the Garmin Training Center software and at If you choose to "share" your runs, you can post them on a blog like I do on mine. (It is probably more information than anyone besides me would care about). Depending on time of day, satellite coverage (which varies slightly during the day), etc., the overall route shown is generally accurate within 30 ft or so. The overall distance run has never been anything but right on. Based on my three months and 40 + runs with it, I would recommend it.


    I'm not a woman, but I will tell you that the 205 and 305 (older models) are a bit bulky. It hasn't bothered me while running, but I do not and would not wear this watch except when I run. The newer Garmin watches like the 405, 410, 610, etc. are less bulky and are closer in size to a "regular" watch. Some of the watches have heart monitors, which many people find helpful (My 205 does not have this feature.) Make sure you review the specs to see if this is included.


    While I cannot directly compare the GPS watch to an Iphone GPS, I can say that I love my GPS watch. It is a key piece of "gear" for me and I use it for every training run and often during races.


    "Whether You Think You Can or Can't, You're Right"-- Henry Ford

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  • lbonney Rookie 21 posts since
    Dec 14, 2007
    Currently Being Moderated
    4. Jun 15, 2011 8:12 AM (in response to NolanShanahan)
    Re: Accuracy of GPS Watches vs. iPhone GPS

    I have used both my Garmin 305 and an Iphone 4 with Imapmyrun for running. I typically only use the phone when I'm running at my daughter's soccer practices so I have my phone with me, and some tunes as well.  I will say that I have had cases where both units have lost signals, and I would say that my experience is that they are equally accurate. I do "trust" my Garmin more and give the choice, that is what I'd pick since it is less cumbersome. Uploading the garmin into Sport tracks gives good results for managing mulit sport and running data.

  • tompor1 Amateur 23 posts since
    Aug 5, 2009
    Currently Being Moderated
    5. Jun 24, 2011 11:35 AM (in response to NolanShanahan)
    Re: Accuracy of GPS Watches vs. iPhone GPS

    I have the Garmin 405 CX which I like, however it has issues and I would not recommend it. It really does not like moisture so when you sweat you get some erattic operation. My suggestion is to stay away from any device that uses the benzel to set functions. I have started wearing a large band-aid under my watch to insulate it from my sweated up wrist. I find the 405cx and my previous Garmin quite accurate and I like the ability to monitor my heart rate so that is a big plus to me.

    I have used my Droid with Run Keeper and Imapmyruns and didn't notice the amount of deviation you report. There is some deviations on all GPS devices I do believe, but overall they do a reasonable job of tracking. The newer one are getting better at maintaining a signal with tree and other cover.

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  • Angela25127 Rookie 4 posts since
    Apr 16, 2009
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    6. Jul 9, 2011 6:34 PM (in response to NolanShanahan)
    Re: Accuracy of GPS Watches vs. iPhone GPS

    I am like the first person who posted I have a Garmin 405 and I love it and its accurate, my NikeGPS+ was always off or sometimes it would not pick up. I haven't had any problems with my Garmin, and I love I can log my stats and I can see the map of my run and I can share my runs if I choose. You can run with or without the heart rate monitor strap and you can get a foot pod for inside running.

  • NancyLFreeman Legend 243 posts since
    Feb 17, 2010
    Currently Being Moderated
    7. Jul 9, 2011 7:22 PM (in response to Katie21784)
    Re: Accuracy of GPS Watches vs. iPhone GPS



    I have a Garmin 110 Forerunner, and it's not bulky at all, just feels like a large watch.  It has limited functionality compared to the larger models, but it's sufficient for me and simple to use.


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  • Rusty Squire Rookie 2 posts since
    Oct 2, 2010
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    8. Aug 2, 2011 9:04 PM (in response to NolanShanahan)
    Re: Accuracy of GPS Watches vs. iPhone GPS

    I use a Garmin 610 watch and a Garmin Edge 800 bike computer and, while they can vary a slight amount on distance, I have never experienced any of the inaccuracies you describe in the mapping with these devices. Of course Garmin is a little bit more of a serious GPS company than Apple because of their presence in aviation and marine navigation.


    I would be shocked if you did not get increased accuracy with a Garmin product. Ryan Hall used the Garmin 210 to pace himself to the fastest marathon ever run by a US male this year in Boston.


    The technology behind GPS are receiver chips that gather location data (latitude and longitude) regularly and store that data in the watches memory. Realistically, the technology in cell phones should be similar, but since being a GPS device is not the primary purpose of an iPhone, or Droid, it is likely that inferior quality equipment gets deployed to save on cost as compared to a Garmin GPS fitness instrument.


    If you just run then I’d take a look at the Garmin 210. If you run and bike and do other sports where miles per hour speed data is required then I’d look at the Garmin 610.

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  • makanasmom Amateur 12 posts since
    Mar 2, 2011
    Currently Being Moderated
    9. Aug 10, 2011 3:00 PM (in response to NolanShanahan)
    Re: Accuracy of GPS Watches vs. iPhone GPS

    I used iMapMyRun for a while and noticed that it was inaccurate so I got walkmeter. It was expensive as far as apps go, but the GPS seems more accurate than any of the other free or 1.99 apps. It works pretty great for me, and I am able to have voice prompt at certain distances or times etc to let me know how I am doing. I keep thinking that I might want to get a gps watch, but I'm not sure I want to invest in a watch that I won't end up using, especially since I run with my phone all the time for safety reasons.

  • LPARafael Pro 166 posts since
    Sep 13, 2010
    Currently Being Moderated
    10. Aug 11, 2011 12:50 PM (in response to NolanShanahan)
    Re: Accuracy of GPS Watches vs. iPhone GPS

    Since I only have an iPhone and not a GPS watch, I cannot compare between the two.  I will throw in that I have not had any problems with the iPhone, nor any of the programs I use.  For running I use either the Nike+ GPS and/or RunKeeper.  I have also used EveryTrail and Motion-X GPS for hiking.  Guess I walk or run slow enough that the GPS solution is more than accurate enough for me.

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  • J Todd Spradlin Rookie 3 posts since
    Aug 8, 2010
    Currently Being Moderated
    11. Sep 13, 2011 12:33 AM (in response to NolanShanahan)
    Accuracy of GPS Watches vs. iPhone GPS

    When I used my iPhone and Nike+GPS app I also noted significant inaccuracy and loss of signal on trail runs.  A few months ago I bought a Garmin FR 610 watch and have been very pleased with it.  It's not cheap but it's very accurate.  I've never had problems with signal loss even in heavily wooded areas, though it sometimes takes a few minutes before the run to lock on to a GPS signal. I use the 610 with a footpod and heart rate monitor.  Seeing all of the data and route on GarminConnect is great.

  • VirginiaBreeze Pro 104 posts since
    Apr 22, 2011
    Currently Being Moderated
    12. Sep 15, 2011 2:15 AM (in response to NolanShanahan)
    Accuracy of GPS Watches vs. iPhone GPS

    I'm sometimes annoyed with the inaccuracy of the Nike+ GPS app and I'm about to purchase a Garmin.  I found that the reviews at were extremely helpful and he has done some pretty exhaustive testing about the accuracy of these devices and I'm convinced that it is much better than the Nike+ application.


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  • Kristy in NC Pro 134 posts since
    Feb 14, 2011
    Currently Being Moderated
    13. Sep 15, 2011 4:19 AM (in response to NolanShanahan)
    Accuracy of GPS Watches vs. iPhone GPS

    I just got a Garmin Forerunner 310.  I decided on this one because DH has it and loves it.  He has not noticed any inaccuracies, it has run seamless and given good information.  I was trying to save money by using my phone, but realized how inaccurate it is when I did a run with him.  Our data was very different - including pace and distance.  Since I'm trying hard to increase my time I wanted accuracy.  We found his on Craig's List for an unbelievable price.  I got mine at Beach at the best price I could find anywhere.

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  • rhonda rhonda Amateur 10 posts since
    Sep 14, 2011
    Currently Being Moderated
    14. Sep 15, 2011 5:06 AM (in response to NolanShanahan)
    Accuracy of GPS Watches vs. iPhone GPS

    I've had a Garmin ForeRunner 301 for a few years and I'm happy with it. Accuracy is good, it's rarely more than 100m off in a 5k or 10k race. Once in a while it'll lose signal, generally under heavy tree cover or in an "urban canyon" with very tall buildings all around. It's also water resistant - I initially found this product while looking for a gift for my sister, who is a rower; anything she carried was at risk of being dunked. I took my GPS swimming once (although it loses satellite reception instantly on going underwater) and kayaking several times; sweat won't faze it at all. The live display of pace tends to lag. It calculates pace by taking a position point I think every ten seconds and calculating distance/time based on that. If you speed up or slow down it might take 20 seconds to update the pace display correctly.


    It's pretty chunky. It is not a watch, it's a wrist-mounted GPS unit with heart rate monitor, and it doesn't pretend to be a watch. I only wear it while running.



    I currently have it programmed with my training schedule, via the computer. I go outside, pick "today's workouts" from the menu, and then start the workout. It beeps at me to speed up or slow down to stay on my target pace, tells me when to change from warmup to tempo or speedwork, and how far (or how long, if it's a time-based segment) I have to go for the current segment, and "presses the lap button" for me when transitioning between segments, which is handy when doing speed work.

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