Accuracy of Garmin 500 and 310XT

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2010-10-06 8:32 AM

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Subject: Accuracy of Garmin 500 and 310XT
I wrote a thread a while back and mentioned there seemed to be a difference in mile recorded for the Garmin 500 versus 310XT. I do expect some standard error, but for some reason the 310XT seems to always few alittle short when compared to the garmin 500. I did reset each one and also both are updated. Wanted to see what people thought about the following miles recorded for each one and if you think they are within standard error?


            Garmin 500               Garmin 310XT
Miles        50.49                           49.82
                55.1                             54.69
                 11.99                          11.74
                 17.47                           16.97
                 30.03                           29.15

As you can see, the 310XT seems always less than the 500. Maybe that is to be expected.

2010-10-06 9:21 AM
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Subject: RE: Accuracy of Garmin 500 and 310XT
Interesting info.  Do you know what the actual distance was of the route?  I think that is a very important stat to include in this comparison.
2010-10-06 9:34 AM
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Subject: RE: Accuracy of Garmin 500 and 310XT
I've found the distances on my 310XT to be very accurate when I'm on routes where I'm certain of the distance.  However, I have found that it overstates elevation gain and--probably as a result of that, actually--also calories.
2010-10-06 10:12 AM
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Subject: RE: Accuracy of Garmin 500 and 310XT
I have both 500 and 310xt. I used to ride with both when I first got my 500 to see the difference.

I don't really care about distance but power so I haven't really tracked it.

Why would it be expected 500 would have less mileage than 310xt?

From my understanding the 500 elevation should be more accurate than 310xt.
2010-10-06 10:12 AM
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Subject: RE: Accuracy of Garmin 500 and 310XT
Unfortuately I don't have the true miles as I ride on off paths so not sure. As for altitude, the Garmin 500 is definitely what i go by as it uses barometric pressure as opposed to the 310XT which uses GPS (less accurate).
2010-10-06 10:14 AM
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Subject: RE: Accuracy of Garmin 500 and 310XT
My HM this past weekend measured 13.19mi. on my 310XT.

No idea whether that's "acceptable" or not.  It just "is".

2010-10-06 10:21 AM
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Subject: RE: Accuracy of Garmin 500 and 310XT
nc452010 - 2010-10-06 10:14 AMMy HM this past weekend measured 13.19mi. on my 310XT.

No idea whether that's "acceptable" or not.  It just "is".
That is due to not running a perfect course (if it was certified). The certification measures the most direct route from start to finish. Think geometry class and the shortest distance between two points being a straight line.
2010-10-06 10:57 AM
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Subject: RE: Accuracy of Garmin 500 and 310XT
jvanis - 2010-10-06 10:21 AM
nc452010 - 2010-10-06 10:14 AMMy HM this past weekend measured 13.19mi. on my 310XT.

No idea whether that's "acceptable" or not.  It just "is".
That is due to not running a perfect course (if it was certified). The certification measures the most direct route from start to finish. Think geometry class and the shortest distance between two points being a straight line.


While I'm sure that's part of it, the 310 gives me slightly different numbers from time to time for the exact same routes that I run. And my footsteps are ingrained in this places, so I know I'm running the same course. :p
2010-10-06 11:26 AM
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Subject: RE: Accuracy of Garmin 500 and 310XT
UWMadTri - 2010-10-06 8:57 AM
jvanis - 2010-10-06 10:21 AM
nc452010 - 2010-10-06 10:14 AMMy HM this past weekend measured 13.19mi. on my 310XT.

No idea whether that's "acceptable" or not.  It just "is".
That is due to not running a perfect course (if it was certified). The certification measures the most direct route from start to finish. Think geometry class and the shortest distance between two points being a straight line.


While I'm sure that's part of it, the 310 gives me slightly different numbers from time to time for the exact same routes that I run. And my footsteps are ingrained in this places, so I know I'm running the same course. :p


Whereas I have not found that to be true with my 310 at all, actually.  Same numbers on same course.
2010-10-06 11:31 AM
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Subject: RE: Accuracy of Garmin 500 and 310XT
I did a couple of runs and a couple of rides this summer wearing two identical Garmin 405's.  I was surprised at how far off they were from each other at times.  150ft off on the runs after a few miles.  A few tenths of a mile off on the bike rides at times.  Often, these differences in the middle of the runs/cycles would somewhat equalize by the end... but what if I had stopped running after 4 miles and never did those other 5?

Overlay the two traces on google earth, and you'll probably see where the differences are.  sharp corners tend not to be picked up very accurately and often get cut off, reducing the 'actual' displayed distance.

but - if you were expecting them to be within 20ft, like it says on the sattelite display- it never seems to work out that way.
2010-10-06 7:14 PM
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Subject: RE: Accuracy of Garmin 500 and 310XT
jvanis - 2010-10-06 11:21 AM
nc452010 - 2010-10-06 10:14 AMMy HM this past weekend measured 13.19mi. on my 310XT.

No idea whether that's "acceptable" or not.  It just "is".
That is due to not running a perfect course (if it was certified). The certification measures the most direct route from start to finish. Think geometry class and the shortest distance between two points being a straight line.


Indeed, running a perfect half-marathon is incredibly difficult unless you're in the very front of the pack.  Different in a tri with less people of course.  This is primarily because the sheer volume of folks in a normal HM mean you're forced to a non-optimal path.

If you're bored some night, I'd encourage you to read the PDF guide on how USATF certifies courses, which includes tons of pictures and examples.  For one I did a post a while ago showing the difference it makes over the course of a race in distance and time if you didn't optimally run it.

Pretty amazing how much time it costs you...

http://www.dcrainmaker.com/2009/03/racing-line-understanding-how-courses.html

2010-10-06 11:19 PM
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Subject: RE: Accuracy of Garmin 500 and 310XT
How is the 500 set to record data?  Is it selectable between 1 second and "smart recording"?  That may be the difference.  The 310XT isn't selectable - if you have a power meter on it is 1sec.  If not it records using smart recording.  That recording mode blips when it detects a significant change in course.  I'll bet your seeing the 310xt miss a bit of distance by not recording a bit of your turns.

When running on a track (odd track with sharper than normal turns) my 310 measures at about 96% of actual distance.  It truncates the turns a tad.

The 500 will be much more accurate on altitude due to the barometric altimeter.
2010-10-07 12:02 AM
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Subject: RE: Accuracy of Garmin 500 and 310XT
tcovert - 2010-10-06 11:26 AM
UWMadTri - 2010-10-06 8:57 AM
jvanis - 2010-10-06 10:21 AM
nc452010 - 2010-10-06 10:14 AMMy HM this past weekend measured 13.19mi. on my 310XT.

No idea whether that's "acceptable" or not.  It just "is".
That is due to not running a perfect course (if it was certified). The certification measures the most direct route from start to finish. Think geometry class and the shortest distance between two points being a straight line.


While I'm sure that's part of it, the 310 gives me slightly different numbers from time to time for the exact same routes that I run. And my footsteps are ingrained in this places, so I know I'm running the same course. :p


Whereas I have not found that to be true with my 310 at all, actually.  Same numbers on same course.


Actually just happened to me over the past 3 days. Ran the exact some course and had readings of:



(Screen shot 2010-10-07 at 12.00.38 AM.png)



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2010-10-07 7:20 AM
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Subject: RE: Accuracy of Garmin 500 and 310XT
test them walking around a track for 1 mile and running on the track for one mile
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