Garmin vs IPhone GPS Accuracy

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2012-09-14 7:05 AM

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Expert
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Subject: Garmin vs IPhone GPS Accuracy
I run with a buddy every once in a while wearing my Garmin 305, and his IPhone always registers about 2% further in total distance. On yesterday's run, according to my watch we finished at 7.33 miles (8:33 min/mile avg). His IPhone registered 7.55 miles (8:17 avg). Anyone have an opinion about which is more accurate? Both units measured an hour and two minutes total time.

2012-09-14 7:08 AM
in reply to: #4410958

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Subject: RE: Garmin vs IPhone GPS Accuracy

I sometimes run with both my Garmin 910 and my Iphone with Endomondo.  They are usually pretty close but if I zoom in on the Endomondo workout it seems like it jumps around a little bit adding distance but not time.

A few weeks ago I did a track workout, just 4 miles around the track and my Garmin was dead on, but my Iphone was indicating mile splits at the wrong times.  I know that 4 laps is a mile on the track and my Iphone was off by 25 meters - 50 meters per mile.

 

2012-09-14 7:43 AM
in reply to: #4410958

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Subject: RE: Garmin vs IPhone GPS Accuracy
i've got miles all over the place, nike, micoach, garmin. I run with my brother and we thought nike was short on garmin but found that most of the error was in the fact that we were running side by side. Inside track outside track kinda deal makes a big difference and route to route as well. You wouldnt think that a couple feet to either side would make a big difference but it did for us. 
2012-09-14 7:46 AM
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Subject: RE: Garmin vs IPhone GPS Accuracy

On average, I would tend to go with the Garmin.  But remember, neither device is going to be consistently accurate--except with time.

2012-09-14 8:06 AM
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Wichita
Subject: RE: Garmin vs IPhone GPS Accuracy
iPhones have a tendency to lose signal and are not as accurate with their GPS.  A buddy and I ran 10 miles on a course we know is 10 miles, at the end mine was up maybe .01 and his was off 1.0.  I'm actually surprised his was as close to your as it was.
2012-09-14 8:34 AM
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Subject: RE: Garmin vs IPhone GPS Accuracy

I've dealt with the accuracy of the iPhone GPS at the programming level just a bit and I would go with Garmin over the iPhone.  If your phone is not able to get a GPS satellite signal for some reason it wil try to determine your location by wi-fi or triangulating off cellular towers.  Triangulating off the cellular towers can throw off the distance by quite a bit.  The algorithms to try and compensate for this can get very complex and are never 100% accurate.

2012-09-14 9:06 AM
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Subject: RE: Garmin vs IPhone GPS Accuracy
I would guess the Garmin is more correct. I have done a run with my iPhone and had MapMyRun, Endmondo, and Strava running and the three apps could not agree on distance. They where all different and even different on elevation. A decent tool to start with but I am planning to upgrade to a Garmin and hoping to be more accurate.
2012-09-14 9:38 AM
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Subject: RE: Garmin vs IPhone GPS Accuracy
I would rank IPhone as third in accuracy after Garmin, Droid based google device gps, etc. I've had them all. I'm sure all the IT geniuses may disagree but that's what I've found. I've used garmin on certified courses and distances, the 305, and it's accurate.
2012-09-14 9:45 AM
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Subject: RE: Garmin vs IPhone GPS Accuracy

DV 1 - 2012-09-14 8:05 AM On yesterday's run, according to my watch we finished at 7.33 miles (8:33 min/mile avg). His IPhone registered 7.55 miles (8:17 avg).

Definitely the iPhone.

 

2012-09-14 10:00 AM
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Alpharetta, Georgia
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Subject: RE: Garmin vs IPhone GPS Accuracy
My only experience using BOTH - my sister and I did a ~20 mile ride together this summer. She had the Edmondo app on her iPhone and I had my Garmin 310 on. At the end they both had the exact same distance and time. 
2012-09-14 10:43 AM
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Subject: RE: Garmin vs IPhone GPS Accuracy

taylorz13 - 2012-09-14 10:38 AM I would rank IPhone as third in accuracy after Garmin, Droid based google device gps, etc. I've had them all. I'm sure all the IT geniuses may disagree but that's what I've found. I've used garmin on certified courses and distances, the 305, and it's accurate.

No offense, but just because it measures accurately on a given day & course does not mean that every time you use it it will provide accuracy.  NO GPS will be perfectly accurate on a consistent basis.  That said, generally, they will be fairly accurate (accurate enough for all but the sticklers for our purposes).  The same goes for the iPhone's GPS (though I believe it relies to a greater extent on software for error correction).  But, depending on conditions (visibility to satellites) and route (lots of small turns require much better tracking to measure accurately), either can be off.  To the plus or minus.

2012-09-14 11:02 AM
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Subject: RE: Garmin vs IPhone GPS Accuracy
They use different GPS chipsets - the iPhone uses a BroadCOM BCM4750 and the Garmin uses a SiRFStar 3 or 4 chipset, which are both consumer grade chips.  I think the largest difference in the two is how and where you wear them.  You might get a better lock with the watch than you do with the phone if the phone is in a pack on your back.  If it's on your arm and not on your back, I would assume it would get a similar lock as the watch.  I guess a 'scientific' test is in order, and you'll have to do some tests and get back to us with the results!  Laughing
2012-09-14 11:53 AM
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Subject: RE: Garmin vs IPhone GPS Accuracy
Goosedog - 2012-09-14 10:45 AM

DV 1 - 2012-09-14 8:05 AM On yesterday's run, according to my watch we finished at 7.33 miles (8:33 min/mile avg). His IPhone registered 7.55 miles (8:17 avg).

Definitely the iPhone.

 

beat me to it!

2012-09-14 3:27 PM
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Subject: RE: Garmin vs IPhone GPS Accuracy
I've had issues with the iPhone GPS on a few occasions. The first time it could have been due to an application fault, using one of those runkeeper programs. I set out on the run and I somehow was running at a 3:30 pace! Sorry, I'm not a Nigerian marathon runner. Within 15 minutes, I had supposedly run 3 miles. I switched apps to MapMyRun, which I use now. Even then, I can run the same 6.2 mile loop and it will give me three different distances on different days, ranging from 6.1 to 6.4.
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