Forums >General Running>10% Error w/ GPS
Wow, I knew GPS was inaccurate but didn't realize how big the margin of error was. This indicates that GPS is likely overestimating the distance of each run by as much as 10%!
http://www.runnersworld.com/gps-watches/why-your-gps-watch-is-probably-overestimating-your-mileage?cid=soc_Runner%27s%20World%20-%20RunnersWorld_FBPAGE_Runner%E2%80%99s%20World__News_RunningGear
But have no fear, because. Math.
Yeah,I read that, but is that really everyone's experience? Is everyone's garmin measuring every 10k race as 11k? Mine doesn't. It's generally +/- 250 meters on a certified 10k course.
they deliberately used a shitty device for this study (at least, according to the article), so the message is really more "crappy device is crappy! Click on our content!"
(mta: I think the people who did the study are proposing a change to how gps measures distance, just the runnersworld take was as above )
2 things to keep in mind:
1.) Runners World is shit.
2.) Decent GPS watches are off by less than 1%.
Runners run
King of PhotoShop
The GPS will always measure long, always. They are not 100% accurate. But ten percent is ridiculous. Spareribs
In my general experience, the garmin GPS is usually off by at most 0.20 to 0.30 miles over 26.2 miles in a marathon... and that's including my not-quite-perfect running of tangents. so, it's approximately 1% at worst. Not too bad for a tiny wristwatch communicating with distant satellites to measure you daily jaunt.
finnegan begin again
Go to your local track, watch on left wrist, stay tight on the 1st lane, hit lap feature at each lap. review for elevation and distance. Varies.
Now measure with a wheel 20 times, varies.
Run a race in a city with tall buildings and review the map afterwards. Makes you look like SuperGirl flying around.
Technology
"... the harder the conflict, the more glorious the triumph. What we obtain too cheap, we esteem too lightly: it is dearness only that gives every thing its value..." Thomas Paine Dec 23, 1776 The Crisis
Adversity is the first path to truth. Lord Byron
"No one plans to fail…..they fail to plan" Skinny Pete
If you're worried about it, just run 10% farther. Problem solved.
But then, I guess, you would have to run an additional 10% of that 10% as well, just to be sure.
We are the music makers,
And we are the dreamers of dreams,
Wandering by lone sea-breakers,
And sitting by desolate streams;
World-losers and world-forsakers,
On whom the pale moon gleams:
Yet we are the movers and shakers
Of the world for ever, it seems.
2 things to keep in mind: 1.) Runners World is shit. 2.) Decent GPS watches are off by less than 1%.
Certainly Mike is correct about #2. ;-) On very large sample sets Garmin Forerunners are off by < 1% on average (with reasonably tight variance, too).
- Joe
We are fragile creatures on collision with our judgment day.
You're right- I haven't experienced discrepancies in races that were that bad.
I know my anal self though and I am probably going to start adding tenths to all my training miles.
Not always, actually. But yes, the mean error is positive in "my experience". I know geometrically what I'm saying seems impossible, but there is more to this than just connecting the dots, at least for some vendors of gps-enabled training devices.
You're right- I haven't experienced discrepancies in races that were that bad. I know my anal self though and I am probably going to start adding tenths to all my training miles.
Because I am just a little bit to anal about my training log, I always chop off the last digit for my training log, e.g., "10.36" becomes "10.3", and I figure those little tenths will all add up and make sure my total lifetime mileage is not over-reported. :-)
hundredths, I mean.
Because I am just a little bit to anal about my training log, I always chop off the last digit for my training log,
MY FINGER! MY BLOODY, BLOODY FINGER!
Feeling the growl again
“However, we deliberately used a very, very low quality device, because we wanted the error to be visible,” he said.
Given that statement, why make any comparisons back to a quality device?
Because I have run the same routes for years and know the mile marks by heart, having GPS'd them a hundred times, I do pick up relatively infrequent occasions when the device makes a noticeable error. For whatever reason, it is typically early in the run, even though I did not start until a lock was obtained. But it's a few hundredths of a mile and by the end of an 8-10 mile run that's not significant.
"If you want to be a bad a$s, then do what a bad a$s does. There's your pep talk for today. Go Run." -- Slo_Hand
I am spaniel - Crusher of Treadmills
not bad for mile 25
Solves the problem of skin being in the way of HR detection.
Mmmmm...beer
We expect a lot from our relatively inexpensive commercial devices that sync up with a signal from outer space.
-Dave
My running blog
Goals | sub-18 5k | sub-3 marathon 2:56:46!!